2021/06/22 更新

写真b

ナカヤマ ユウ
中山 優
NAKAYAMA Yu
*大学が定期的に情報更新している項目(その他は、researchmapの登録情報を転載)
所属*
理学部 物理学科
理学研究科 物理学専攻博士課程後期課程
理学研究科 物理学専攻博士課程前期課程
職名*
准教授
学位
博士(理学) ( 東京大学 )
研究テーマ*
  • 場の量子論や超弦理論で生まれてきた最新の理論物理学の道具を使って、理論物理学の普遍的な枠組みを理解し、その理論的応用を考えることを研究テーマとする。具体的には、共形ブートストラップ法を用いた臨界現象の研究、ゲージ・重力対応に基づく量子重力理論と繰り込み群の研究など、ミクロな世界からマクロな世界まで統一的に理解したいと考えている。

  • 学内職務経歴*
    • 2016年4月 - 現在 
      理学部   物理学科   准教授
    • 2016年4月 - 現在 
      理学研究科   物理学専攻博士課程前期課程   准教授
    • 2016年4月 - 現在 
      理学研究科   物理学専攻博士課程後期課程   准教授
     

    研究分野

    • 自然科学一般 / 素粒子、原子核、宇宙線、宇宙物理にする理論

    経歴

    • 2016年4月 - 現在 
      立教大学   理学部 物理学科   准教授

      詳細を見る

    • 2016年4月 - 現在 
      立教大学   理学研究科 物理学専攻博士課程後期課程   准教授

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    • 2016年4月 - 現在 
      立教大学   理学研究科 物理学専攻博士課程前期課程   准教授

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    学歴

    • - 2007年3月 
      東京大学   理学系研究科

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      国名: 日本国

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    • - 2007年3月 
      東京大学   理学系研究科

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      国名: 日本国

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    • - 2002年3月 
      東京大学   理学部

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      国名: 日本国

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    論文

    • Efimov effect at the Kardar-Parisi-Zhang roughening transition

      Yu Nakayama, Yusuke Nishida

          2020年10月28日

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      Surface growth governed by the Kardar-Parisi-Zhang (KPZ) equation in
      dimensions higher than two undergoes a roughening transition from smooth to
      rough phases with increasing the nonlinearity. It is also known that the KPZ
      equation can be mapped onto quantum mechanics of attractive bosons with a
      contact interaction, where the roughening transition corresponds to a binding
      transition of two bosons with increasing the attraction. Such critical bosons
      in three dimensions actually exhibit the Efimov effect, where a three-boson
      coupling turns out to be relevant under the renormalization group so as to
      break the scale invariance down to discrete one. On the basis of these facts
      linking the two distinct subjects in physics, we predict that the KPZ
      roughening transition in three dimensions shows either the discrete scale
      invariance or no intrinsic scale invariance.

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      その他リンク: http://arxiv.org/pdf/2010.15161v1

    • Anomalous hydrodynamics with dyonic charge

      Yu Nakayama

          2020年9月30日

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      We study anomalous hydrodynamics with a dyonic charge. We show that the local
      second law of thermodynamics constrains the structure of the anomaly in
      addition to the structure of the hydrodynamic constitutive equations. In
      particular, we show that not only the usual $E\cdot B$ term but also $E^2 -B^2$
      term should be present in the anomaly with a specific coefficient for the local
      entropy production to be positive definite.

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      その他リンク: http://arxiv.org/pdf/2009.14360v1

    • Conformal invariance from scale invariance in non-linear sigma models

      Yu Nakayama

          2020年6月9日

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      There exists a certain argument that in even dimensions, scale invariant
      quantum field theories are conformal invariant. We may try to extend the
      argument in $2n + \epsilon$ dimensions, but the naive extension has a small
      loophole, which indeed shows an obstruction in non-linear sigma models in
      $2+\epsilon$ dimensions. Even though it could have failed due to the loophole,
      we show that scale invariance does imply conformal invariance of non-linear
      sigma models in $2+\epsilon$ dimension from the seminal work by Perelman on the
      Ricci flow.

      DOI: 10.1103/PhysRevD.102.065018

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      その他リンク: http://arxiv.org/pdf/2006.05070v1

    • Bootstrap bound on extremal Reissner-Nordström black hole in AdS

      Yu Nakayama

          2020年4月17日

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      Based on the numerical conformal bootstrap bound, we show that the
      arbitrarily small Reissner-Nordstr\"om black hole in AdS space-time is
      inconsistent with holography unless the energy spectrum is modified quantum
      mechanically or it is unstable as indicated by the weak gravity conjecture.

      DOI: 10.1016/j.physletb.2020.135677

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      その他リンク: http://arxiv.org/pdf/2004.08069v1

    • On fermionic minimal models

      Chang-Tse Hsieh, Yu Nakayama, Yuji Tachikawa

          2020年2月27日

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      We show that there is a fermionic minimal model, i.e. a 1+1d conformal field
      theory which contains operators of half-integral spins in its spectrum, for
      each $c=1-6/m(m+1)$, $m\ge 3$. This generalizes the Majorana fermion for
      $c=1/2$, $m=3$ and the smallest $\mathcal{N}{=}1$ supersymmetric minimal model
      for $c=7/10$, $m=4$. We provide explicit Hamiltonians on Majorana chains
      realizing these fermionic minimal models.

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      その他リンク: http://arxiv.org/pdf/2002.12283v1

    • CP-violating super Weyl anomaly

      Koichiro Nakagawa, Yu Nakayama

          2020年2月4日

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      In CP-violating conformal field theories in four dimensions, the Pontryagin
      density can appear in the Weyl anomaly. The Pontryagin density in the Weyl
      anomaly is consistent, but it has a peculiar feature that the parent
      three-point function of the energy-momentum tensor can violate CP only
      (semi-)locally. In this paper, we study the supersymmetric completion of the
      Pontryagin density in the Weyl anomaly, where the central charge $c$
      effectively becomes a complex number. The supersymmetry suggests that it
      accompanies the graviphoton $\theta$ term associated with the R-symmetry
      gauging in the Weyl anomaly. It also accompanies new CP-violating terms in the
      R-current anomaly. While there are no conclusive perturbative examples of
      CP-violating super Weyl anomaly, we construct explicit supersymmetric dilaton
      effective action which generates these anomalies.

      DOI: 10.1103/PhysRevD.101.105013

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      その他リンク: http://arxiv.org/pdf/2002.01128v2

    • On Duality in $\mathcal{N}=2$ supersymmetric Liouville Theory

      Yu Nakayama

          2020年1月30日

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      Similarly to the bosonic Liouville theory, the $\mathcal{N}=2$ supersymmetric
      Liouville theory was conjectured to be equipped with the duality that exchanges
      the superpotential and the K\"ahler potential. The conjectured duality,
      however, seems to suffer from a mismatch of the preserved symmetries. More than
      fifteen years ago, when I was a student, my supervisor Tohru Eguchi gave a
      beautiful resolution of the puzzle when the supersymmetry is enhanced to
      $\mathcal{N}=4$ based on his insight into the underlying geometric structure of
      the $A_1$ singularity. I will review his unpublished but insightful idea and
      present our attempts to extend it to more general cases.

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      その他リンク: http://arxiv.org/pdf/2001.11157v2

    • Exclusion Inside or at the Border of Conformal Bootstrap Continent

      Yu Nakayama

          2019年12月26日

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      How large can anomalous dimensions be in conformal field theories? What can
      we do to attain larger values? One attempt to obtain large anomalous dimensions
      efficiently is to use the Pauli exclusion principle. Certain operators
      constructed out of constituent fermions cannot form bound states without
      introducing non-trivial excitations. To assess the efficiency of this
      mechanism, we compare them with the numerical conformal bootstrap bound as well
      as with other interacting field theory examples. In two dimensions, it turns
      out to be the most efficient: it saturates the bound and is located at the
      (second) kink. In higher dimensions, it more or less saturates the bound but it
      may be slightly inside.

      DOI: 10.1142/S0217751X20500360

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      その他リンク: http://arxiv.org/pdf/1912.11748v2

    • Critical gravity from four dimensional scale invariant gravity

      Ariel Edery, Yu Nakayama

          2019年8月23日

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      We show that a critical condition exists in four dimensional scale invariant
      gravity given by the pure quadratic action $\beta \,C_{\mu\nu\sigma\rho}
      C^{\mu\nu\sigma \rho} + \alpha \,R^2$ where $C^{\mu}_{\,\,\nu \sigma \rho}$ is
      the Weyl tensor, $R$ is the Ricci scalar and $\beta$ and $\alpha$ are
      dimensionless parameters. The critical condition in a dS or AdS background is
      $\beta =6 \alpha$. This leads to critical gravity where the massive spin two
      physical ghost becomes a massless spin two graviton. In contrast to the
      original work on critical gravity, no Einstein gravity with a cosmological
      constant is added explicitly to the higher-derivative action. The critical
      condition is obtained in two independent ways. In the first case, we show the
      equivalence between the initial action and an action containing Einstein
      gravity, a cosmological constant, a massless scalar field plus Weyl squared
      gravity. The scale invariance is spontaneously broken. The linearized
      Einstein-Weyl equations about a dS or AdS background yield the critical
      condition $\beta=6\alpha$. In the second case, we work directly with the
      original quadratic action. After a suitable field redefinition, where the
      metric perturbation is traceless and transverse, we obtain linearized equations
      about a dS or AdS background that yield the critical condition $\beta=
      6\alpha$. As in the first case, we also obtain a propagating massless scalar
      field. Substituting $\beta=6\alpha$ into the energy and entropy formula for the
      Schwarzschild and Kerr AdS or dS black hole in higher-derivative gravity yields
      zero, the same value obtained in the original work on critical gravity. We
      discuss the role of boundary conditions in relaxing the $\beta=6\alpha$
      condition.

      DOI: 10.1007/JHEP11(2019)169

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      その他リンク: http://arxiv.org/pdf/1908.08778v2

    • Conformal Contact Terms and Semi-Local Terms

      Yu Nakayama

          2019年6月19日

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      We study conformal properties of local terms such as contact terms and
      semi-local terms in correlation functions of a conformal field theory. Not all
      of them are universal observables but they do appear in physically important
      correlation functions such as (anomalous) Ward-Takahashi identities or
      Schwinger-Dynson equations. We develop some tools such as embedding space delta
      functions and effective action to examine conformal invariance of these local
      terms.

      DOI: 10.1007/s00023-020-00951-z

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      その他リンク: http://arxiv.org/pdf/1906.07914v2

    • Holographic Dual of Conformal Field Theories with Very Special $T\bar{J}$ Deformations

      Yu Nakayama

          2019年5月14日

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      Very special $T\bar{J}$ deformations of a conformal field theory are
      irrelevant deformations that break the Lorentz symmetry but preserve the
      twisted Lorentz symmetry. We construct a holographic description of very
      special $T\bar{J}$ deformations. We give a holographic recipe to study the
      double trace as well as single trace deformations. The former is obtained from
      the change of the boundary condition while the latter is obtained from the
      change of the supergravity background.

      DOI: 10.1103/PhysRevD.100.086011

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      その他リンク: http://arxiv.org/pdf/1905.05353v1

    • Palatini formulation of pure $R^2$ gravity yields Einstein gravity with no massless scalar

      Ariel Edery, Yu Nakayama

          2019年2月21日

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      Pure $R^2$ gravity has been shown to be equivalent to Einstein gravity with
      non-zero cosmological constant and a massless scalar field. We show that the
      Palatini formulation of pure $R^2$ gravity is equivalent to Einstein gravity
      with non-zero cosmological constant as before but with no massless scalar
      field. This is an important new development because the massless scalar field
      is not readily identifiable with any known particle in nature or unknown
      particles like cold dark matter which are expected to be massive. We then
      include a non-minimally coupled Higgs field as well as fermions to discuss how
      the rest of the standard model fields fit into this paradigm. With Higgs field,
      Weyl invariance is maintained by using a hybrid formalism that includes both
      the Palatini curvature scalar $\mathcal{R}$ and the usual Ricci scalar $R$

      DOI: 10.1103/PhysRevD.99.124018

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      その他リンク: http://arxiv.org/pdf/1902.07876v2

    • Conformal equations that are not Virasoro or Weyl invariant

      Yu Nakayama

          2019年2月14日

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      While the argument by Zamolodchikov and Polchinski suggests global conformal
      invariance implies Virasoro invariance in two-dimensional unitary conformal
      field theories with discrete dilatation spectrum, it is not the case in more
      general situations without these assumptions. We indeed show that almost all
      the globally conformal invariant differential equations in two dimensions are
      neither Virasoro invariant nor Weyl invariant. The only exceptions are the
      higher spin conservation laws, conformal Killing tensor equations and the
      Laplace equation of a conformal scalar.

      DOI: 10.1007/s11005-019-01186-8

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      その他リンク: http://arxiv.org/pdf/1902.05273v2

    • Very Special $T\bar{J}$ deformed CFT

      Yu Nakayama

          2018年11月6日

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      We study a very special class of $T\bar{J}$ deformations of conformal field
      theories in two dimensions. While the deformations break the Lorentz symmetry,
      they preserve the twisted Lorentz symmetry. The resulting theory has
      right-moving Virasoro as well as left-moving translation and left-moving
      (chiral) scale symmetry without left-moving special conformal symmetry (nor
      left-moving Virasoro symmetry). As in the original $T\bar{J}$ deformations,
      they may be regarded as an operator dependent non-local change of coordinates.
      We show concrete examples based on worldsheet string theory and discuss how the
      non-unitary nature enables us to circumvent various no-go theorems.

      DOI: 10.1103/PhysRevD.99.085008

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      その他リンク: http://arxiv.org/pdf/1811.02173v1

    • Boundary and Defect CFT: Open Problems and Applications

      Natan Andrei, Agnese Bissi, Matthew Buican, John Cardy, Patrick Dorey, Nadav Drukker, Johanna Erdmenger, Daniel Friedan, Dmitri Fursaev, Anatoly Konechny, Charlotte Kristjansen, Isao Makabe, Yu Nakayama, Andy O'Bannon, Robert Parini, Brandon Robinson, Shinsei Ryu, Cornelius Schmidt-Colinet, Volker Schomerus, Christoph Schweigert, Gerard Watts

          2018年10月12日

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      Proceedings of the workshop "Boundary and Defect Conformal Field Theory: Open
      Problems and Applications," Chicheley Hall, Buckinghamshire, UK, 7-8 Sept.
      2017.

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      その他リンク: http://arxiv.org/pdf/1810.05697v1

    • Gravity Dual for Very Special Conformal Field Theories in type IIB Supergravity

      Yu Nakayama

          2018年7月24日

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      We study holographic dual descriptions of very special conformal field
      theories with the T(2) symmetry. After constructing solutions in effective five
      dimensional Einstein gravity coupled with massive two-form fields, we uplift
      them to the ten dimensional type IIB supergravity, via a consistent truncation
      ansatz, to derive new analytical solutions in string theory. From the
      Kaluza-Klein ansatz in terms of the internal Sasaki-Einstein space, we obtain
      their field theory interpretation with concrete realizations in a large class
      of holographic $\mathcal{N}=1$ supersymmetric conformal field theories. Null
      compactification of these theories yields holographic dual descriptions of
      non-relativistic critical systems with translational invariance but without
      rotational invariance such as the ones induced from a constant electromagnetic
      field.

      DOI: 10.1016/j.physletb.2018.09.051

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      その他リンク: http://arxiv.org/pdf/1807.08882v1

    • Gravitating magnetic monopole via the spontaneous symmetry breaking of pure $R^2$ gravity

      Ariel Edery, Yu Nakayama

          2018年7月18日

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      The pure $R^2$ gravity is equivalent to Einstein gravity with cosmological
      constant and a massless scalar field and it further possesses the so-called
      restricted Weyl symmetry which is a symmetry larger than scale symmetry. To
      incorporate matter, we consider a restricted Weyl invariant action composed of
      pure $R^2$ gravity, SU(2) Yang-Mills fields and a non-minimally coupled
      massless Higgs field (a triplet of scalars). When the restricted Weyl symmetry
      is spontaneously broken, it is equivalent to an Einstein-Yang-Mills-Higgs
      (EYMH) action with a cosmological constant and a massive Higgs non-minimally
      coupled to gravity i.e. via a term $\tilde{\xi} R |\Phi|^2$. When the
      restricted Weyl symmetry is not spontaneously broken, linearization about
      Minkowski space-time does not yield gravitons in the original $R^2$ gravity and
      hence it does not gravitate. However, we show that in the broken gauge sector
      of our theory, where the Higgs field acquires a non-zero vacuum expectation
      value, Minkowski space-time is a viable gravitating background solution. We
      then obtain numerically gravitating magnetic monopole solutions for non-zero
      coupling constant $\tilde{\xi}=1/6$ in three different backgrounds: Minkowski,
      anti-de Sitter (AdS) and de Sitter (dS), all of which are realized in our
      restricted Weyl invariant theory.

      DOI: 10.1103/PhysRevD.98.064011

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      その他リンク: http://arxiv.org/pdf/1807.07004v2

    • On the realization of impossible anomalies

      Yu Nakayama

          2018年4月9日

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      The Wess-Zumino consistency condition allows more exotic forms of anomalies
      than those we usually encounter. For example in two-dimensional conformal field
      theories in the curved background with space-time dependent coupling constant
      $\lambda^i(x)$, a $U(1)$ current could possess anomalous divergence of the form
      $D^\mu J_\mu = \tilde{c} R + \chi_{ij} \partial^\mu \lambda^i
      \partial_\mu\lambda_j + \tilde{\chi}_{ij} \epsilon^{\mu\nu} \partial_\mu
      \lambda^i \partial_\nu \lambda^j + \cdots $. Another example is the CP odd
      Pontryagin density in four-dimensional Weyl anomaly. We could, however, argue
      that they are impossible in conformal field theories because they cannot
      correspond to any (unregularized) conformally invariant correlation functions.
      We find that this no-go argument may be a red herring. We show that some of
      these impossible anomalies avoid the no-go argument because they are not
      primary operators, and the others circumvent it because they are realized as
      semi-local terms as is the case with the conformally invariant Green-Schwartz
      mechanism and in the higher dimensional analogue of Liouville or linear dilaton
      theory.

      DOI: 10.1103/PhysRevD.98.085002

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      その他リンク: http://arxiv.org/pdf/1804.02940v1

    • Local field theory construction of Very Special Conformal Symmetry

      Yu Nakayama

          2018年2月19日

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      Cohen and Glashow argued that very special conformal field theories of a
      particular kind (i.e. with HOM(2) or SIM(2) invariance) cannot be constructed
      within the framework of local field theories. We, however, show examples of
      local construction by using non-linear realization. We further construct linear
      realization from the topological twist at the cost of unitarity. To demonstrate
      the ubiquity of our idea, we also present corresponding holographic models.

      DOI: 10.1103/PhysRevD.98.025007

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      その他リンク: http://arxiv.org/pdf/1802.06489v2

    • Three ways to solve critical $φ^4$ theory on $4-ε$ dimensional real projective space: perturbation, bootstrap, and Schwinger-Dyson equation

      Chika Hasegawa, Yu Nakayama

          2018年1月27日

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      We solve the two-point function of the lowest dimensional scalar operator in
      the critical $\phi^4$ theory on $4-\epsilon$ dimensional real projective space
      in three different methods. The first is to use the conventional perturbation
      theory, and the second is to impose the crosscap bootstrap equation, and the
      third is to solve the Schwinger-Dyson equation under the assumption of
      conformal invariance. We find that the three methods lead to mutually
      consistent results but each has its own advantage.

      DOI: 10.1142/S0217751X18500495

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      その他リンク: http://arxiv.org/pdf/1801.09107v3

    • Cancelling Weyl anomaly from position dependent coupling

      Yu Nakayama

          2017年11月17日

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      Once we put a quantum field theory on a curved manifold, it is natural to
      further assume that coupling constants are position dependent. The position
      dependent coupling constants then provide an extra contribution to the Weyl
      anomaly so that we may attempt to cancel the entire Weyl anomaly on the curved
      manifold. We show that such a cancellation is possible for constant Weyl
      transformation or infinitesimal but generic Weyl transformation in two and four
      dimensional conformal field theories with exactly marginal deformations. When
      the Weyl scaling factor is annihilated by conformal powers of Laplacian (e.g.
      by Fradkin-Tseytlin-Riegert-Paneitz operator in four dimensions), the
      cancellation persists even at the finite order thanks to a nice mathematical
      property of the $Q$-curvature under the Weyl transformation.

      DOI: 10.1103/PhysRevD.97.045008

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      その他リンク: http://arxiv.org/pdf/1711.06413v2

    • Characterization of degenerate supersymmetric ground states of the Nicolai supersymmetric fermion lattice model by symmetry breakdown

      Hosho Katsura, Hajime Moriya, Yu Nakayama

          2017年10月12日

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      We study a supersymmetric fermion lattice model defined by Hermann Nicolai.
      We show that its infinitely many classical supersymmetric ground states are
      associated to breakdown of hidden local supersymmetries.

      DOI: 10.1088/1751-8121/ab9916

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      その他リンク: http://arxiv.org/pdf/1710.04385v2

    • Very Special Conformal Field Theories (VSCFT) and their holographic duals

      Yu Nakayama

          2017年7月18日

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      Cohen and Glashow introduced the notion of very special relativity as viable
      space-time symmetry of elementary particle physics. As a natural generalization
      of their idea, we study the subgroup of the conformal group, dubbed very
      special conformal symmetry, which is an extension of the very special
      relativity. We classify all of them and construct field theory examples as well
      as holographic realization of the very special conformal field theories.

      DOI: 10.1103/PhysRevD.97.065003

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      その他リンク: http://arxiv.org/pdf/1707.05423v2

    • Nature of chiral phase transition in two-flavor QCD

      K. -I. Ishikawa, Y. Iwasaki, Yu Nakayama, T. Yoshie

          2017年6月25日

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      We investigate the nature of the chiral phase transition in the massless
      two-flavor QCD using the renormalization group improved gauge action and the
      Wilson quark action on $32^3\times 16$, $24^3\times 12$, and $16^3\times 8$
      lattices. We calculate the spacial and temporal propagators of the iso-triplet
      mesons in the pseudo-scalar ($PS$), scalar ($S$), vector ($V$) and axial-vector
      ($AV$) channels on the lattice of three sizes. We first verify that the RG
      scaling is excellently satisfied for all cases. This is consistent with the
      claim that the chiral phase transition is second order. Then we compare the
      spacial and temporal effective masses between the axial partners, i.e. $PS$ vs
      $S$ and $V$ vs $AV$, on each of the three size lattices. We find the effective
      masses of all of six cases for the axial partners agree remarkably. This is
      consistent with the claim that at least $Z_4$ subgroup of the $U_A(1)$ symmetry
      in addition to the $SU_A(2)$ symmetry is recovered at the chiral phase
      transition point.

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      その他リンク: http://arxiv.org/pdf/1706.08872v1

    • Bootstrap experiments on higher dimensional CFTs

      Yu Nakayama

          2017年5月8日

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      Recent programs on conformal bootstrap suggest an empirical relationship
      between the existence of non-trivial conformal field theories and non-trivial
      features such as a kink in the unitarity bound of conformal dimensions in the
      conformal bootstrap equations. We report the existene of non-trivial kinks in
      the unitarity bound of scalar operators in the adjoint representation of the
      $SU(N)$ symmetric conformal field theories. They have interesting properties
      (1) the kinks exist in $d<6$ dimensions (2) the location of kinks are when the
      unitarity bound hits the space-time dimension $d$ (3) there exists a "conformal
      window" of $N<N_*$, where $N_* \sim 15 $ in $d=4$ and $N_* \sim 20$ in $d=5$.

      DOI: 10.1142/S0217751X18500367

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      その他リンク: http://arxiv.org/pdf/1705.02744v1

    • RG scaling relations at chiral phase transition in two-flavor QCD

      K. -I. Ishikawa, Y. Iwasaki, Yu Nakayama, T. Yoshie

          2017年4月11日

      詳細を見る

      We investigate the nature of the chiral phase transition in the massless
      two-flavor QCD using the renormalization group improved gauge action and the
      Wilson quark action on $32^3\times 16$, $24^3\times 12$, and $16^3\times 8$
      lattices. Based on the renormalization group equation, we derive the scaling
      relation for the effective masses of mesons at the chiral phase transition
      point. If the chiral phase transition is second order, the effective masses as
      a function of the rescaled time/space do not depend on the lattice size and
      show the universal behavior. We find that our numerical simulations on the
      three sizes of lattices are excellently on the scaling curves, which is
      consistent with the second order phase transition.

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      その他リンク: http://arxiv.org/pdf/1704.03134v1

    • Can we change $c$ in four-dimensional CFTs by exactly marginal deformations?

      Yu Nakayama

          2017年2月8日

      詳細を見る

      There is no known obstructions, but we have not been aware of any concrete
      examples, either. The Wess-Zumino consistency condition for the conformal
      anomaly says that $a$ cannot change but does not say anything about $c$. In
      supersymmetric models, both $a$ and $c$ are determined from the triangle
      t'Hooft anomalies and the unitarity demands that both must be fixed, so the
      unitary supersymmetric conformal field theories do not admit such a
      possibility. Given this field theory situation, we construct an effective
      AdS/CFT model without supersymmetry in which $c$ changes under exactly marginal
      deformations. So, yes, we can.

      DOI: 10.1007/JHEP07(2017)004

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      その他リンク: http://arxiv.org/pdf/1702.02324v2

    • Supersymmetry breaking and Nambu-Goldstone fermions with cubic dispersion

      Noriaki Sannomiya, Hosho Katsura, Yu Nakayama

          2016年12月7日

      詳細を見る

      We introduce a lattice fermion model in one spatial dimension with
      supersymmetry (SUSY) but without particle number conservation. The Hamiltonian
      is defined as the anticommutator of two nilpotent supercharges $Q$ and
      $Q^\dagger$. Each supercharge is built solely from spinless fermion operators
      and depends on a parameter $g$. The system is strongly interacting for small
      $g$, and in the extreme limit $g=0$, the number of zero-energy ground states
      grows exponentially with the system size. By contrast, in the large-$g$ limit,
      the system is non-interacting and SUSY is broken spontaneously. We study the
      model for modest values of $g$ and show that under certain conditions
      spontaneous SUSY breaking occurs in both finite and infinite chains. We analyze
      the low-energy excitations both analytically and numerically. Our analysis
      suggests that the Nambu-Goldstone fermions accompanying the spontaneous SUSY
      breaking have cubic dispersion at low energies.

      DOI: 10.1103/PhysRevD.95.065001

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      その他リンク: http://arxiv.org/pdf/1612.02285v3

    • Interacting scale but non-conformal field theories

      Yu Nakayama

          2016年11月30日

      詳細を見る

      There is a dilemma in constructing interacting scale invariant but not
      conformal invariant Euclidean field theories. On one hand, scale invariance
      without conformal invariance seems more generic by requiring only a smaller
      symmetry. On the other hand, the existence of a non-conserved current with
      exact scaling dimension $d-1$ in $d$ dimensions seems to require extra
      fine-tuning. To understand the competition better, we explore some examples
      without the reflection positivity. We show that a theory of elasticity (a.k.a
      Riva-Cardy theory) coupled with massless fermions in $d=4-\epsilon$ dimensions
      does not possess an interacting scale invariant fixed point except for unstable
      (and unphysical) one with an infinite coefficient of compression. We do,
      however, find interacting scale invariant but non-conformal field theories in
      gauge fixed versions of the Banks-Zaks fixed points in $d=4$ dimensions.

      DOI: 10.1103/PhysRevD.95.065016

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      その他リンク: http://arxiv.org/pdf/1611.10040v2

    • $ε$-Expansion in Critical $φ^3$-Theory on Real Projective Space from Conformal Field Theory

      Chika Hasegawa, Yu Nakayama

          2016年11月19日

      詳細を見る

      We use a compatibility between the conformal symmetry and the equations of
      motion to solve the one-point function in the critical $\phi^3$-theory (a.k.a
      the critical Lee-Yang model) on the $d = 6 - \epsilon$ dimensional real
      projective space to the first non-trivial order in the $\epsilon$-expansion. It
      reproduces the conventional perturbation theory and agrees with the numerical
      conformal bootstrap result.

      DOI: 10.1142/S0217732317500456

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      その他リンク: http://arxiv.org/pdf/1611.06373v2

    • Euclidean M-theory background dual to three-dimensional scale invariant field theory without conformal invariance

      Yu Nakayama

          2016年8月8日

      詳細を見る

      We show that eleven dimensional supergravity in Euclidean signature admits an
      exact classical solution with isometry corresponding to a three dimensional
      scale invariant field theory without conformal invariance. We also construct
      the holographic renormalization group flow that connects the known UV conformal
      fixed point and the new scale invariant but not conformal fixed point. In view
      of holography, the existence of such classical solutions suggests that the
      topologically twisted M2-brane gauge theory possesses a scale invariant but not
      conformal phase.

      DOI: 10.1103/PhysRevD.95.046006

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      その他リンク: http://arxiv.org/pdf/1608.02651v2

    • Supersymmetry breaking and Nambu-Goldstone fermions in an extended Nicolai model

      Noriaki Sannomiya, Hosho Katsura, Yu Nakayama

          2016年6月13日

      詳細を見る

      We study a model of interacting spinless fermions in a one dimensional
      lattice with supersymmetry (SUSY). The Hamiltonian is given by the
      anti-commutator of two supercharges $Q$ and $Q^\dagger$, each of which is
      comprised solely of fermion operators and possesses one adjustable parameter
      $g$. When the parameter $g$ vanishes, the model is identical to the one studied
      by Nicolai [H. Nicolai, J. Phys. A: Math. Gen. \textbf{9}, 1497 (1976)], where
      the zero-energy ground state is exponentially degenerate. On the other hand, in
      the large-$g$ limit the model reduces to the free-fermion chain with a
      four-fold degenerate ground state. We show that for finite chains SUSY is
      spontaneously broken when $g > 0$. We also rigorously prove that for
      sufficiently large $g$ the ground-state energy density is nonvanishing in the
      infinite-volume limit. We further analyze the nature of the low-energy
      excitations by employing various techniques such as rigorous inequalities,
      exact numerical diagonalization, and renormalization group method with
      bosonization. The analysis reveals that the low-energy excitations are
      described by massless Dirac fermions (or Thirring fermions more generally),
      which can be thought of as Nambu-Goldstone fermions from the spontaneous SUSY
      breaking.

      DOI: 10.1103/PhysRevD.94.045014

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      その他リンク: http://arxiv.org/pdf/1606.03947v2

    • Topologically twisted renormalization group flow and its holographic dual

      Yu Nakayama

          2016年6月7日

      詳細を見る

      Euclidean field theories admit more general deformations than usually
      discussed in quantum field theories because of mixing between rotational
      symmetry and internal symmetry (a.k.a topological twist). Such deformations may
      be relevant, and if the subsequent renormalization group flow leads to a
      non-trivial fixed point, it generically gives rise to a scale invariant
      Euclidean field theory without conformal invariance. Motivated by an ansatz
      studied in cosmological models some time ago, we develop a holographic dual
      description of such renormalization group flows in the context of AdS/CFT. We
      argue that the non-trivial fixed points require fine-tuning of the bulk theory
      in general, but remarkably we find that the $O(3)$ Yang-Mills theory coupled
      with the four-dimensional Einstein gravity in the minimal manner supports such
      a background with the Euclidean AdS metric.

      DOI: 10.1103/PhysRevD.95.066010

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      その他リンク: http://arxiv.org/pdf/1606.01988v1

    • Bootstrap bound for conformal multi-flavor QCD on lattice

      Yu Nakayama

          2016年5月13日

      詳細を見る

      The recent work by Iha et al shows an upper bound on mass anomalous dimension
      $\gamma_m$ of multi-flavor massless QCD at the renormalization group fixed
      point from the conformal bootstrap in $SU(N_F)_V$ symmetric conformal field
      theories under the assumption that the fixed point is realizable with the
      lattice regularization based on staggered fermions. We show that the almost
      identical but slightly stronger bound applies to the regularization based on
      Wilson fermions (or domain wall fermions) by studying the conformal bootstrap
      in $SU(N_f)_L \times SU(N_f)_R$ symmetric conformal field theories. For
      $N_f=8$, our bound implies $\gamma_m < 1.31$ to avoid dangerously irrelevant
      operators that are not compatible with the lattice symmetry.

      DOI: 10.1007/JHEP07(2016)038

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      その他リンク: http://arxiv.org/pdf/1605.04052v2

    • Bulk Local States and Crosscaps in Holographic CFT

      Yu Nakayama, Hirosi Ooguri

          2016年5月2日

      詳細を見る

      In a weakly coupled gravity theory in the anti-de Sitter space, local states
      in the bulk are linear superpositions of Ishibashi states for a crosscap in the
      dual conformal field theory. The superposition structure can be constrained
      either by the microscopic causality in the bulk gravity or the bootstrap
      condition in the boundary conformal field theory. We show, contrary to some
      expectation, that these two conditions are not compatible to each other in the
      weak gravity regime. We also present an evidence to show that bulk local states
      in three dimensions are not organized by the Virasoro symmetry.

      DOI: 10.1007/JHEP10(2016)085

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      その他リンク: http://arxiv.org/pdf/1605.00334v1

    • Hidden global conformal symmetry without Virasoro extension in theory of elasticity

      Yu Nakayama

          2016年4月4日

      詳細を見る

      The theory of elasticity (a.k.a. Riva-Cardy model) has been regarded as an
      example of scale invariant but not conformal field theories. We argue that in
      $d=2$ dimensions, the theory has hidden global conformal symmetry of
      $SL(2,\mathbb{R}) \times SL(2,\mathbb{R})$ without its Virasoro extension. More
      precisely, we can embed all the correlation functions of the displacement
      vector into a global conformal field theory with four-derivative action in
      terms of two scalar potential variables, which necessarily violates the
      reflection positivity. The energy-momentum tensor for the potential variables
      cannot be improved to become traceless so that it does not show the Virasoro
      symmetry even with the existence of global special conformal current.

      DOI: 10.1016/j.aop.2016.06.010

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      その他リンク: http://arxiv.org/pdf/1604.00810v2

    • Conformal Bootstrap Dashing Hopes of Emergent Symmetry

      Yu Nakayama, Tomoki Ohtsuki

          2016年2月23日

      詳細を見る

      We use the conformal bootstrap program to derive necessary conditions for
      emergent symmetry enhancement from discrete symmetry (e.g. $\mathbb{Z}_n$) to
      continuous symmetry (e.g. $U(1)$) under the renormalization group flow. In
      three dimensions, in order for $\mathbb{Z}_2$ symmetry to be enhanced to $U(1)$
      symmetry, the conformal bootstrap program predicts that the scaling dimension
      of the order parameter field at the infrared conformal fixed point must satisfy
      $\Delta_1 > 1.08$. We also obtain the similar conditions for $\mathbb{Z}_3$
      symmetry with $\Delta_{1} > 0.580$ and $\mathbb{Z}_4$ symmetry with $\Delta_1 >
      0.504$ from the simultaneous conformal bootstrap analysis of multiple
      four-point functions. Our necessary conditions impose severe constraints on
      many controversial physics such as the chiral phase transition in QCD, the
      deconfinement criticality in N\'eel-VBS transitions and anisotropic
      deformations in critical $O(n)$ models. In some cases, we find that the
      conformal bootstrap program dashes hopes of emergent symmetry enhancement
      proposed in the literature.

      DOI: 10.1103/PhysRevLett.117.131601

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      その他リンク: http://arxiv.org/pdf/1602.07295v2

    • Bootstrapping critical Ising model on three-dimensional real projective space

      Yu Nakayama

          2016年1月25日

      詳細を見る

      Given a conformal data on a flat Euclidean space, we use crosscap conformal
      bootstrap equations to numerically solve the Lee-Yang model as well as the
      critical Ising model on a three-dimensional real projective space. We check the
      rapid convergence of our bootstrap program in two-dimensions from the exact
      solutions available. Based on the comparison, we estimate that our systematic
      error on the numerically solved one-point functions of the critical Ising model
      on a three-dimensional real projective space is less than one percent. Our
      method opens up a novel way to solve conformal field theories on non-trivial
      geometries.

      DOI: 10.1103/PhysRevLett.116.141602

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      その他リンク: http://arxiv.org/pdf/1601.06851v2

    • Non-trivial Center Dominance in High Temperature QCD

      K. -I. Ishikawa, Y. Iwasaki, Yu Nakayama, T. Yoshie

          2015年11月11日

      詳細を見る

      We investigate the properties of quarks and gluons above the chiral phase
      transition temperature $T_c,$ using the RG improved gauge action and the Wilson
      quark action with two degenerate quarks mainly on a $32^3\times 16$ lattice. In
      the one-loop perturbation theory, the thermal ensemble is dominated by the
      gauge configurations with effectively $Z(3)$ center twisted boundary
      conditions, making the thermal expectation value of the spatial Polyakov loop
      take a non-trivial $Z(3)$ center. This is in agreement with our lattice
      simulation of high temperature QCD. We further observe that the temporal
      propagator of massless quarks at extremely high temperature $\beta=100.0 \, (T
      \simeq10^{58} T_c)$ remarkably agrees with the temporal propagator of free
      quarks with the $Z(3)$ twisted boundary condition for $t/L_t \geq 0.2$, but
      differs from that with the $Z(3)$ trivial boundary condition. As we increase
      the mass of quarks $m_q$, we find that the thermal ensemble continues to be
      dominated by the $Z(3)$ twisted gauge field configurations as long as $m_q \le
      3.0 \, T$ and above that the $Z(3)$ trivial configurations come in. The
      transition is essentially identical to what we found in the departure from the
      conformal region in the zero-temperature many-flavor conformal QCD on a finite
      lattice by increasing the mass of quarks. We argue that the behavior is
      consistent with the renormalization group analysis at finite temperature.

      DOI: 10.1142/S0217732316501509

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      その他リンク: http://arxiv.org/pdf/1511.03411v3

    • Reheating of the Universe as holographic thermalization

      Shinsuke Kawai, Yu Nakayama

          2015年9月15日

      詳細を見る

      Assuming gauge/gravity correspondence we study reheating of the Universe
      using its holographic dual. Inflaton decay and thermalisation of the decay
      products correspond to collapse of a spherical shell and formation of a
      blackhole in the dual anti-de Sitter (AdS) spacetime. The reheating temperature
      is computed as the Hawking temperature of the developed blackhole probed by a
      dynamical boundary, and is determined by the inflaton energy density and the
      AdS radius, with corrections from the dynamics of the shell collapse. For given
      initial energy density of the inflaton field the holographic model gives
      significantly lower reheating temperature than the instant reheating scenario,
      while it is shown to be safely within phenomenological bounds.

      DOI: 10.1016/j.physletb.2016.06.019

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      その他リンク: http://arxiv.org/pdf/1509.04661v1

    • Weak Gravity Conjecture in AdS/CFT

      Yu Nakayama, Yasunori Nomura

          2015年9月5日

      詳細を見る

      We study implications of the weak gravity conjecture in the AdS/CFT
      correspondence. Unlike in Minkowski spacetime, AdS spacetime has a physical
      length scale, so that the conjecture must be generalized with an additional
      parameter. We discuss possible generalizations and translate them into the
      language of dual CFTs, which take the form of inequalities involving the
      dimension and charge of an operator as well as the current and energy-momentum
      tensor central charges. We then test these inequalities against various CFTs to
      see if they are universally obeyed by all the CFTs. We find that certain CFTs,
      such as supersymmetric QCDs, do not satisfy them even in the large $N$ limit.
      This does not contradict the conjecture in AdS spacetime because the theories
      violating them are either unlikely or unclear to have weakly coupled
      gravitational descriptions, but it suggests that the CFT inequalities obtained
      here by naive translations do not apply beyond the regime in which weakly
      coupled gravitational descriptions are available.

      DOI: 10.1103/PhysRevD.92.126006

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      その他リンク: http://arxiv.org/pdf/1509.01647v2

    • Bulk Locality and Boundary Creating Operators

      Yu Nakayama, Hirosi Ooguri

          2015年7月15日

      詳細を見る

      We formulate a minimum requirement for CFT operators to be localized in the
      dual AdS. In any spacetime dimensions, we show that a general solution to the
      requirement is a linear superposition of operators creating spherical
      boundaries in CFT, with the dilatation by the imaginary unit from their
      centers. This generalizes the recent proposal by Miyaji et al. for bulk local
      operators in the three dimensional AdS. We show that Ishibashi states for the
      global conformal symmetry in any dimensions and with the imaginary dilatation
      obey free field equations in AdS and that incorporating bulk interactions
      require their superpositions. We also comment on the recent proposals by Kabat
      et al., and by H. Verlinde.

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      その他リンク: http://arxiv.org/pdf/1507.04130v1

    • Strong gauging or decoupling ghost matter

      Yu Nakayama

          2015年6月17日

      詳細を見る

      Gauging extra matter is a common way to couple two CFTs discontinuously. We
      may consider gauging matter by strongly coupled gauge theories at criticality
      rather than by weakly coupled (asymptotic free) gauge theories. It often
      triggers relevant deformations and possibly leads to a non-trivial fixed point.
      In many examples such as the IR limit of SQCDs (and their variants), the
      relevant RG flow induced by this strong gauging makes the total central charge
      $a$ increase rather than decrease compared with the sum of the original
      decoupled CFTs. The dilaton effective field theory argument given by
      Komargodski and Schwimmer does not apply because strong gauging is not a simple
      deformation by operators in the original two decoupled CFTs and it may not be
      UV complete. When the added matter is vector-like, one may emulate strong
      gauging in a UV completed manner by decoupling of ghost matter. While the UV
      completed description makes the dilaton effective field theory argument
      possible, due to the non-unitarity, we cannot conclude the positivity of the
      central charge difference in accordance with the observations in various
      examples that show the contrary.

      DOI: 10.1142/S0217751X15501559

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      その他リンク: http://arxiv.org/pdf/1506.05208v1

    • IR fixed points in $SU(3)$ gauge Theories

      K. -I. Ishikawa, Y. Iwasaki, Yu Nakayama, Y. Yoshie

          2015年3月9日

      詳細を見る

      We propose a novel RG method to specify the location of the IR fixed point in
      lattice gauge theories and apply it to the $SU(3)$ gauge theories with $N_f$
      fundamental fermions. It is based on the scaling behavior of the propagator
      through the RG analysis with a finite IR cut-off, which we cannot remove in the
      conformal field theories in sharp contrast with the confining theories. The
      method also enables us to estimate the anomalous mass dimension in the
      continuum limit at the IR fixed point. We perform the program for $N_f=16, 12,
      8 $ and $N_f=7$ and indeed identify the location of the IR fixed points in all
      cases.

      DOI: 10.1016/j.physletb.2015.07.019

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      その他リンク: http://arxiv.org/pdf/1503.02359v2

    • Local renormalization group functions from quantum renormalization group and holographic bulk locality

      Yu Nakayama

          2015年2月25日

      詳細を見る

      The bulk locality in the constructive holographic renormalization group
      requires miraculous cancellations among various local renormalization group
      functions. The cancellation is not only from the properties of the spectrum but
      from more detailed aspects of operator product expansions in relation to
      conformal anomaly. It is remarkable that one-loop computation of the universal
      local renormalization group functions in the weakly coupled limit of the
      $\mathcal{N}=4$ super Yang-Mills theory fulfils the necessary condition for the
      cancellation in the strongly coupled limit in its $SL(2,\mathbf{Z})$ duality
      invariant form. From the consistency between the quantum renormalization group
      and the holographic renormalization group, we determine some unexplored local
      renormalization group functions (e.g. diffusive term in the beta function for
      the gauge coupling constant) in the strongly coupled limit of the planar
      $\mathcal{N}=4$ super Yang-Mills theory.

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      その他リンク: http://arxiv.org/pdf/1502.07049v2

    • Generating Einstein gravity, cosmological constant and Higgs mass from restricted Weyl invariance

      Ariel Edery, Yu Nakayama

          2015年2月20日

      詳細を見る

      Recently, it has been pointed out that dimensionless actions in four
      dimensional curved spacetime possess a symmetry which goes beyond scale
      invariance but is smaller than full Weyl invariance. This symmetry was dubbed
      {\it restricted Weyl invariance}. We show that starting with a restricted Weyl
      invariant action that includes a Higgs sector with no explicit mass, one can
      generate the Einstein-Hilbert action with cosmological constant and a Higgs
      mass. The model also contains an extra massless scalar field which couples to
      the Higgs field (and gravity). If the coupling of this extra scalar field to
      the Higgs field is negligibly small, this fixes the coefficient of the
      nonminimal coupling $R \Phi^2$ between the Higgs field and gravity. Besides the
      Higgs sector, all the other fields of the standard model can be incorporated
      into the original restricted Weyl invariant action.

      DOI: 10.1142/S0217732315501527

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      その他リンク: http://arxiv.org/pdf/1502.05932v1

    • Perturbative search for dead-end CFTs

      Yu Nakayama

          2015年1月9日

      詳細を見る

      To explore the possibility of self-organized criticality, we look for CFTs
      without any relevant scalar deformations (a.k.a dead-end CFTs) within
      power-counting renormalizable quantum field theories with a weakly coupled
      Lagrangian description. In three dimensions, the only candidates are pure
      (Abelian) gauge theories, which may be further deformed by Chern-Simons terms.
      In four dimensions, we show that there are infinitely many non-trivial
      candidates based on chiral gauge theories. Using the three-loop beta functions,
      we compute the gap of scaling dimensions above the marginal value, and it can
      be as small as $\mathcal{O}(10^{-5})$ and robust against the perturbative
      corrections. These classes of candidates are very weakly coupled and our
      perturbative conclusion seems difficult to refute. Thus, the hypothesis that
      non-trivial dead-end CFTs do not exist is likely to be false in four
      dimensions.

      DOI: 10.1007/JHEP05(2015)046

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      その他リンク: http://arxiv.org/pdf/1501.02280v2

    • Is cosmological constant screened in Liouville gravity with matter?

      Takeo Inami, Yoji Koyama, Yu Nakayama, Mariko Suzuki

          2014年12月7日

      詳細を見る

      There has been a proposal that infrared quantum effects of massless
      interacting field theories in de-Sitter space may provide time-dependent
      screening of the cosmological constant. As a concrete model of the proposal, we
      study the three loop corrections to the energy-momentum tensor of massless
      $\lambda \phi^4$ theory in the background of classical Liouville gravity in
      $D=2$ dimensional de-Sitter space. We find that the cosmological constant is
      screened in sharp contrast to the massless $\lambda \phi^4$ theory in $D=4$
      dimensions due to the sign difference between the cosmological constant of the
      Liouville gravity and that of the Einstein gravity. To argue for the robustness
      of our prediction, we introduce the concept of time-dependent infrared
      counter-terms and examine if they recover the de-Sitter invariance in the
      $\lambda \phi^4$ theory in comparison with the Sine-Gordon model where it was
      possible.

      DOI: 10.1093/ptep/ptv062

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      その他リンク: http://arxiv.org/pdf/1412.2350v2

    • Imaginary supergravity or Virial supergravity?

      Yu Nakayama

          2014年11月4日

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      When a globally supersymmetric theory is scale invariant, it must possess a
      Virial supercurrent supermultiplet. The multiplet structure is analogous to the
      R-current supermultiplet in globally R-symmetric theories but we put extra
      "$i$"s in various formulae. We construct a novel type of supergravity from
      gauging the Virial supercurrent supermultiplet in $d=1+3$ dimensions. We give
      the full non-linear superspace action with the help of a covariantly linear
      unitary superconformal compensator. The resulting supergravity is peculiar: (1)
      no Einstein-like second order kinetic term is allowed without matter (2) there
      exists a dynamical non-geometrical connection (3) the metric is unimodular in
      the Wess-Zumino gauge and can be coupled only to scale invariant matter.
      Examples of matter couplings and higher derivative kinetic terms are studied
      from the superconformal approach. Our work completes the classification of the
      irreducible $\mathcal{N}=1$ supergravities in $d=1+3$ dimensions.

      DOI: 10.1016/j.nuclphysb.2015.01.012

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      その他リンク: http://arxiv.org/pdf/1411.1057v1

    • Bootstrapping phase transitions in QCD and frustrated spin systems

      Yu Nakayama, Tomoki Ohtsuki

          2014年7月23日

      詳細を見る

      In view of its physical importance in predicting the order of chiral phase
      transitions in QCD and frustrated spin systems, we perform the conformal
      bootstrap program of $O(n)\times O(2)$-symmetric conformal field theories in
      $d=3$ dimensions with a special focus on $n=3$ and $4$. The existence of
      renormalization group fixed points with these symmetries has been controversial
      over years, but our conformal bootstrap program provides the non-perturbative
      evidence. In both $n=3$ and $4$ cases, we find singular behaviors in the bounds
      of scaling dimensions of operators in two different sectors, which we claim
      correspond to chiral and collinear fixed points, respectively. In contrast to
      the cases with larger values of $n$, we find no evidence for the anti-chiral
      fixed point. Our results indicate the possibility that the chiral phase
      transitions in QCD and frustrated spin systems are continuous with the critical
      exponents that we predict from the conformal bootstrap program.

      DOI: 10.1103/PhysRevD.91.021901

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      その他リンク: http://arxiv.org/pdf/1407.6195v2

    • Restricted Weyl invariance in four-dimensional curved spacetime

      Ariel Edery, Yu Nakayama

          2014年5月31日

      詳細を見る

      We discuss the physics of {\it restricted Weyl invariance}, a symmetry of
      dimensionless actions in four dimensional curved space time. When we study a
      scalar field nonminimally coupled to gravity with Weyl(conformal) weight of
      $-1$ (i.e. scalar field with the usual two-derivative kinetic term), we find
      that dimensionless terms are either fully Weyl invariant or are Weyl invariant
      if the conformal factor $\Omega(x)$ obeys the condition
      $g^{\mu\nu}\nabla_{\mu}\nabla_{\nu}\Omega=0$. We refer to the latter as {\it
      restricted Weyl invariance}. We show that all the dimensionless geometric terms
      such as $R^2$, $R_{\mu\nu}R^{\mu\nu}$ and
      $R_{\mu\nu\sigma\tau}R^{\mu\nu\sigma\tau}$ are restricted Weyl invariant.
      Restricted Weyl transformations possesses nice mathematical properties such as
      the existence of a composition and an inverse in four dimensional space-time.
      We exemplify the distinction among rigid Weyl invariance, restricted Weyl
      invariance and the full Weyl invariance in dimensionless actions constructed
      out of scalar fields and vector fields with Weyl weight zero.

      DOI: 10.1103/PhysRevD.90.043007

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      その他リンク: http://arxiv.org/pdf/1406.0060v2

    • Five dimensional $O(N)$-symmetric CFTs from conformal bootstrap

      Yu Nakayama, Tomoki Ohtsuki

          2014年4月21日

      詳細を見る

      We investigate the conformal bootstrap approach to $O(N)$ symmetric CFTs in
      five dimension with particular emphasis on the lower bound on the current
      central charge. The bound has a local minimum for all $N>1$, and in the large
      $N$ limit we propose that the minimum is saturated by the critical $O(N)$
      vector model at the UV fixed point, the existence of which has been recently
      argued by Fei, Giombi, and Klebanov. The location of the minimum is generically
      different from the minimum of the lower bound of the energy-momentum tensor
      central charge when it exists for smaller $N$.
      To better understand the situation, we examine the lower bounds of the
      current central charge of $O(N)$ symmetric CFTs in three dimension to compare.
      We find the similar agreement in the large $N$ limit but the discrepancy for
      smaller $N$ with the other sectors of the conformal bootstrap.

      DOI: 10.1016/j.physletb.2014.05.058

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      その他リンク: http://arxiv.org/pdf/1404.5201v2

    • Approaching conformal window of $O(n)\times O(m)$ symmetric Landau-Ginzburg models from conformal bootstrap

      Yu Nakayama, Tomoki Ohtsuki

          2014年4月2日

      詳細を見る

      $O(n) \times O(m)$ symmetric Landau-Ginzburg models in $d=3$ dimension
      possess a rich structure of the renormalization group and its understanding
      offers a theoretical prediction of the phase diagram in frustrated spin models
      with non-collinear order. Depending on $n$ and $m$, they may show
      chiral/anti-chiral/Heisenberg/Gaussian fixed points within the same
      universality class. We approach all the fixed points in the conformal bootstrap
      program by examining the bound on the conformal dimensions for scalar operators
      as well as non-conserved current operators with consistency crosschecks. For
      large $n/m$, we show strong evidence for the existence of four fixed points by
      comparing the operator spectrum obtained from the conformal bootstrap program
      with that from the large $n/m$ analysis. We propose a novel non-perturbative
      approach to the determination of the conformal window in these models based on
      the conformal bootstrap program. From our numerical results, we predict that
      for $m=3$, $n=7\sim 8$ is the edge of the conformal window for the anti-chiral
      fixed points.

      DOI: 10.1103/PhysRevD.89.126009

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      その他リンク: http://arxiv.org/pdf/1404.0489v3

    • Improvement of energy-momentum tensor and non-Gaussianities in holographic cosmology

      Shinsuke Kawai, Yu Nakayama

          2014年3月25日

      詳細を見る

      In holographic models of cosmology based on the (A)dS/CFT correspondence,
      conformal symmetry is implicit in the dual description of the Universe.
      Generically, however, one cannot expect the (broken) conformal invariance in
      the cosmic fluctuations as only the scale invariance is manifest in
      experiments. Also, in order for the prediction of the holographic models to
      make sense, the conformal symmetry needs to be broken as the scalar mode of the
      metric fluctuations becomes pure gauge in the conformal limit. We discuss the
      improvement ambiguity of the energy-momentum tensor in this context and
      construct a holographic model of the Universe that preserves the scale
      invariance but not necessarily the full conformal invariance. Our sample
      computation using a weakly coupled dual field theory shows that the orthogonal
      type of non-Gaussianity is present over and above the equilateral type. The
      improvement ambiguity corresponds to the choice of the energy momentum tensor
      that will couple to our particle physics sector after inflation. Our results
      show that the holographic prediction of the cosmological parameters crucially
      depends on such a choice.

      DOI: 10.1007/JHEP06(2014)052

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      その他リンク: http://arxiv.org/pdf/1403.6220v1

    • $a-c$ test of holography vs quantum renormalization group

      Yu Nakayama

          2014年1月21日

      詳細を見る

      We show that a "constructive derivation" of the AdS/CFT correspondence based
      on the quantum local renormalization group in large N quantum field theories
      consistently provides the a-c holographic Weyl anomaly in d=4 at the curvature
      squared order in the bulk action. The consistency of the construction further
      predicts the form of the metric beta function.

      DOI: 10.1142/S0217732314501582

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      その他リンク: http://arxiv.org/pdf/1401.5257v3

    • Global Structure of Conformal Theories in the SU(3) Gauge Theory

      K. -I. Ishikawa, Y. Iwasaki, Yu Nakayama, T. Yoshie

          2013年10月18日

      詳細を見る

      We investigate SU(3) gauge theories in four dimensions with Nf fundamental
      fermions, on a lattice using the Wilson fermion. Clarifying the vacuum
      structure in terms of Polyakov loops in spatial directions and properties of
      temporal propagators using a new method "local analysis", we conjecture that
      the "conformal region" exists together with the confining region and the
      deconfining region in the phase structure parametrized by beta and K, both in
      the cases of the large Nf QCD within the conformal window (referred as
      Conformal QCD) with an IR cutoff and small Nf QCD at T/Tc>1 with Tc being the
      chiral transition temperature (referred as High Temperature QCD).
      Our numerical simulation on a lattice of the size 16^3 x 64 shows the
      following evidence of the conjecture. In the conformal region we find the
      vacuum is the nontrivial Z(3) twisted vacuum modified by non-perturbative
      effects and temporal propagators of meson behave at large t as a power-law
      corrected Yukawa-type decaying form. The transition from the conformal region
      to the deconfining region or the confining region is a sharp transition between
      different vacua and therefore it suggests a first order transition both in
      Conformal QCD and in High Temperature QCD.
      Within our fixed lattice simulation, we find that there is a precise
      correspondence between Conformal QCD and High Temperature QCD in the temporal
      propagators under the change of the parameters Nf and T/Tc respectively. In
      particular, we find the correspondence between Conformal QCD with Nf = 7 and
      High Temperature QCD with Nf=2 at T ~ 2 Tc being in close relation to a meson
      unparticle model. From this we estimate the anomalous mass dimension gamma* =
      1.2 (1) for Nf=7. We also show that the asymptotic state in the limit T/Tc -->
      infty is a free quark state in the Z(3) twisted vacuum.

      DOI: 10.1103/PhysRevD.89.114503

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      その他リンク: http://arxiv.org/pdf/1310.5049v3

    • Vector Beta function

      Yu Nakayama

          2013年10月2日

      詳細を見る

      We propose various properties of renormalization group beta functions for
      vector operators in relativistic quantum field theories. We argue that they
      must satisfy compensated gauge invariance, orthogonality with respect to scalar
      beta functions, Higgs-like relation among anomalous dimensions and a gradient
      property. We further conjecture that non-renormalization holds if and only if
      the vector operator is conserved. The local renormalization group analysis
      guarantees the first three within power counting renormalization. We verify all
      the conjectures in conformal perturbation theories and holography in the weakly
      coupled gravity regime.

      DOI: 10.1142/S0217751X13501662

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      その他リンク: http://arxiv.org/pdf/1310.0574v2

    • Consistency of local renormalization group in d=3

      Yu Nakayama

          2013年7月30日

      詳細を見る

      We discuss Weyl anomaly and consistency conditions of local renormalization
      group in d=1+2 dimensional quantum field theories. We give a classification of
      the consistency conditions and ambiguities in most generality within the
      power-counting renormalization scheme. They provide many non-trivial
      constraints on possible forms of beta functions, anomalous dimensions and Weyl
      anomaly of general d=1+2 dimensional quantum field theories. We perform modest
      checks of our results in conformal perturbation theories, supersymmetric field
      theories and holographic computations.

      DOI: 10.1016/j.nuclphysb.2013.12.002

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      その他リンク: http://arxiv.org/pdf/1307.8048v1

    • Holographic interpretation of renormalization group approach to singular perturbations in non-linear differential equations

      Yu Nakayama

          2013年5月17日

      詳細を見る

      We give a holographic explanation how the renormalization group approach to
      singular perturbations in non-linear differential equations proposed by Chen,
      Goldenfeld and Oono is indeed equivalent to a renormalization group method in
      quantum field theories proposed by Gell-Mann and Low via AdS/CFT
      correspondence.

      DOI: 10.1103/PhysRevD.88.105006

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      その他リンク: http://arxiv.org/pdf/1305.4117v2

    • (0,2) Chiral Liouville Field Theory

      Yu Nakayama

          2013年5月16日

      詳細を見る

      As an existence proof of the (0,2) heterotic supercurrent supermultiplets in
      (1+1) dimensional quantum field theories which are consistent with the warped
      superconformal algebra, we construct the (0,2) chiral Liouville field theories.
      The two distinct possibilities of the heterotic supercurrent supermultiplets
      are both realized.

      DOI: 10.1142/S0217732313501782

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      その他リンク: http://arxiv.org/pdf/1305.3680v1

    • Zoology of heterotic supercurrent supermultiplets in d=2

      Yu Nakayama

          2013年5月13日

      詳細を見る

      We present various (0,2) heterotic supercurrent supermultiplets in (1+1)
      dimensional quantum field theories. From the minimal supercurrent
      supermultiplets, we deduce conditions on symmetry enhancement such as Lorentz
      invariance, (chiral) dilatation invariance, R-invariance, (chiral) conformal
      invariance and their various combinations. Our construction covers many
      interesting and/or exotic possibilities such as Lifshitz supersymmetry and
      warped superconformal algebra. We also discuss the corresponding supergravity
      by gauging the supercurrent supermultiplet. In particular, we propose a novel
      class of heterotic supergravity based on the virial supercurrent.

      DOI: 10.1007/JHEP08(2013)049

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      その他リンク: http://arxiv.org/pdf/1305.2937v2

    • Conformal Behavior in QCD

      K. -I. Ishikawa, Y. Iwasaki, Yu Nakayama, T. Yoshie

          2013年4月16日

      詳細を見る

      We give a new perspective on the properties of quarks and gluons at finite
      temperature T in N_f = 2 ~ 6 QCD. We point out the existence of an IR fixed
      point for the gauge coupling constant at T>T_c (T_c is the chiral phase
      transition temperature). Based on this observation we predict theoretically and
      verify numerically that the correlation functions of a meson G(t) at T/T_c > 1
      decay with a power-law corrected Yukawa-type decaying form, G(t)=c exp(-m
      t)/t^alpha in the "conformal region" defined by m < c Lambda_IR, where
      Lambda_IR is the IR cutoff, m is the characteristic scale of the spectrum in
      the meson cannel and c is a constant of order 1. The decaying form is the
      characteristics of conformal theories with an IR cutoff. We discuss in detail
      how the resulting hyper scaling relation of physical observables may modify the
      existing argument about the order of the chiral phase transition in the N_f=2
      case.

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      その他リンク: http://arxiv.org/pdf/1304.4345v4

    • Scale invariance vs conformal invariance

      Yu Nakayama

          2013年2月4日

      詳細を見る

      In this review article, we discuss the distinction and possible equivalence
      between scale invariance and conformal invariance in relativistic quantum field
      theories. Under some technical assumptions, we can prove that scale invariant
      quantum field theories in $d=2$ dimension necessarily possess the enhanced
      conformal symmetry. The use of the conformal symmetry is well appreciated in
      the literature, but the fact that all the scale invariant phenomena in $d=2$
      dimension enjoy the conformal property relies on the deep structure of the
      renormalization group. The outstanding question is whether this feature is
      specific to $d=2$ dimension or it holds in higher dimensions, too. As of
      January 2014, our consensus is that there is no known example of scale
      invariant but non-conformal field theories in $d=4$ dimension under the
      assumptions of (1) unitarity, (2) Poincar\'e invariance (causality), (3)
      discrete spectrum in scaling dimension, (4) existence of scale current and (5)
      unbroken scale invariance in the vacuum. We have a perturbative proof of the
      enhancement of conformal invariance from scale invariance based on the higher
      dimensional analogue of Zamolodchikov's $c$-theorem, but the non-perturbative
      proof is yet to come. As a reference we have tried to collect as many
      interesting examples of scale invariance in relativistic quantum field theories
      as possible in this article. We give a complementary holographic argument based
      on the energy-condition of the gravitational system and the space-time
      diffeomorphism in order to support the claim of the symmetry enhancement. We
      believe that the possible enhancement of conformal invariance from scale
      invariance reveals the sublime nature of the renormalization group and
      space-time with holography.

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      その他リンク: http://arxiv.org/pdf/1302.0884v4

    • Conformal Theories with an IR cutoff

      K. -I. Ishikawa, Y. Iwasaki, Yu Nakayama, T. Yoshie

          2013年1月21日

      詳細を見る

      We give a new perspective on the dynamics of conformal theories realized in
      the SU(N) gauge theory, when the number of flavors N_f is within the conformal
      window. Motivated by the RG argument on conformal theories with a finite IR
      cutoff \Lambda_{IR}, we conjecture that the propagator of a meson G_H(t) on a
      lattice behaves at large t as a power-law corrected Yukawa-type decaying form
      G_H(t) = c_H \exp{(-m_H t)}/t^{\alpha_H} instead of the exponentially decaying
      form c_H\exp{(-m_H t)}, in the small quark mass region where m_H \le c
      \Lambda_{IR}: m_H is the mass of the ground state hadron in the channel H and c
      is a constant of order 1. The transition between the "conformal region" and the
      "confining region" is a first order transition. Our numerical results verify
      the predictions for the N_f=7 case and the N_f=16 case in the SU(3) gauge
      theory with the fundamental representation.

      DOI: 10.1103/PhysRevD.87.071503

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      その他リンク: http://arxiv.org/pdf/1301.4785v4

    • Does anomalous violation of null energy condition invalidate holographic c-theorem?

      Yu Nakayama

          2012年11月19日

      詳細を見る

      Null energy condition plays a crucial role in holographic renormalization
      group flow, leading to the holographic c-theorem. Unfortunately, the null
      energy condition is quantum mechanically violated. Even the averaged version
      can be violated. We discuss how the anomalous violation of the null energy
      condition affects the holographic renormalization group flow in 1+3 dimensional
      bulk gravity. We show that despite the violation of the null energy condition,
      a suitably modified holographic c-function with a peculiar log correction is
      still monotonically decreasing in so far as we add the counterterm that removes
      a ghost mode of gravity.

      DOI: 10.1016/j.physletb.2013.02.023

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      その他リンク: http://arxiv.org/pdf/1211.4628v1

    • Is boundary conformal in CFT?

      Yu Nakayama

          2012年10月24日

      詳細を見る

      We discuss boundary conditions for conformal field theories that preserve the
      boundary Poincare invariance. As in the bulk field theories, a question arises
      whether boundary scale invariance leads to boundary conformal invariance. With
      unitarity, Cardy's condition of vanishing momentum flow is necessary for the
      boundary conformal invariance, but it is not sufficient in general. We show
      both a proof and a counterexample of the enhancement of boundary conformal
      invariance in (1+1) dimension, which depends on the extra assumption we make.
      In (1+2) dimension, Cardy's condition is shown to be sufficient. In higher
      dimensions, we give a perturbative argument in favor of the enhancement based
      on the boundary g-theorem. With the help of the holographic dual recently
      proposed, we show a holographic proof of the boundary conformal invariance
      under the assumption of the boundary strict null energy condition, which also
      gives a sufficient condition for the strong boundary g-theorem.

      DOI: 10.1103/PhysRevD.87.046005

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      その他リンク: http://arxiv.org/pdf/1210.6439v3

    • Supercurrent, Supervirial and Superimprovement

      Yu Nakayama

          2012年8月23日

      詳細を見る

      Supersymmetric field theories possess a rich structure in their supercurrent
      supermultiplets. Some symmetries are manifest in one supercurrent
      supermultiplet but not in the others; for instance, R-symmetry is manifest in
      the R-multiplet but not in the Ferrara-Zumino multiplet. Similarly, we argue
      that dilatation symmetry is manifest in the Virial multiplet (also known as a
      variant minimal supercurrent supermultiplet in the literature). It reveals that
      R-symmetry and dilatation symmetry are conceptually independent without further
      assumptions even though the superconformal symmetry connects the two. We show
      the structure of the Virial multiplet for general renormalizable supersymmetric
      field theories in (1+3) dimension to all orders in perturbation theory, and
      discuss the condition for the dilatation invariance (but not necessarily
      R-symmetric nor superconformal). We present novel scale invariant trajectories
      with a nilpotent structure in coupling constants for non-unitary Wess-Zumino
      models with non-vanishing beta functions, which are, therefore, not
      superconformal.

      DOI: 10.1103/PhysRevD.87.085005

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      その他リンク: http://arxiv.org/pdf/1208.4726v4

    • Intrinsic ambiguity in second order viscosity parameters in relativistic hydrodynamics

      Yu Nakayama

          2012年6月12日

      詳細を見る

      We show that relativistic hydrodynamics in Minkowski space-time has intrinsic
      ambiguity in second order viscosity parameters in the Landau-Lifshitz frame.
      This stems from the possibility of improvements of energy-momentum tensor.
      There exist at least two viscosity parameters which can be removed by using
      this ambiguity in scale invariant hydrodynamics in (1+3) dimension, and
      seemingly non-conformal hydrodynamic theories can be hiddenly conformal
      invariant.

      DOI: 10.1142/S0217751X12501254

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      その他リンク: http://arxiv.org/pdf/1206.2421v1

    • Holographic Renormalization of Foliation Preserving Gravity and Trace Anomaly

      Yu Nakayama

          2012年3月5日

      詳細を見る

      From the holographic renormalizationg group viewpoint, while the scale
      transformation plays a primary role in the duality by providing the extra
      dimension, the special conformal transformation seems to only play a secondary
      role. We, however, claim that the space-time diffeomorphism is crucially
      related to the latter. For its demonstration, we study the holographic
      renormalization group flow of a foliation preserving diffeomophic theory of
      gravity (a.k.a. space-time flipped Horava gravity). We find that the dual field
      theory, if any, is only scale invariant but not conformal invariant. In
      particular, we show that the holographic trace anomaly in four-dimension
      predicts the Ricci scalar squared term that would be incompatible with the
      Wess-Zumino consistency condition if it were conformal. This illustrates how
      the foliation preserving diffeomophic theory of gravity could be inconsistent
      with a theorem of the dual unitary quantum field theory.

      DOI: 10.1007/s10714-012-1427-3

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      その他リンク: http://arxiv.org/pdf/1203.1068v3

    • CP-violating CFT and trace anomaly

      Yu Nakayama

          2012年1月17日

      詳細を見る

      It is logically possible that the trace anomaly in four dimension includes
      the Hirzebruch-Pontryagin density in CP violating theories. Although the term
      vanishes at free conformal fixed points, we realize such a possibility in the
      holographic renormalization group and show that it is indeed possible. The
      Hirzebruch-Pontryagin term in the trace anomaly may serve as a barometer to
      understand how much CP is violated in conformal field theories.

      DOI: 10.1016/j.nuclphysb.2012.02.006

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      その他リンク: http://arxiv.org/pdf/1201.3428v2

    • Gravity Dual for Hofman-Strominger Theorem

      Yu Nakayama

          2011年12月3日

      詳細を見る

      We provide a gravity counterpart of the theorem by Hofman and Strominger that
      in (1+1) dimension, chiral scale invariance indicates chiral conformal
      invariance. We show that the strict null energy condition gives a sufficient
      condition to guarantee the symmetry enhancement. We also investigate a
      possibility to construct holographic c-function that decreases along the
      holographic renormalization group flow.

      DOI: 10.1103/PhysRevD.85.085032

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      その他リンク: http://arxiv.org/pdf/1112.0635v1

    • On ε-conjecture in a-theorem

      Yu Nakayama

          2011年10月12日

      詳細を見る

      The derivation of the a-theorem recently proposed by Komargodski and
      Schwimmer relies on the \epsilon-conjecture that demands decoupling of dilaton
      from the rest of the infrared theory. We point out that the decoupling, if
      true, provides a strong evidence for the equivalence between scale invariance
      and conformal invariance in four dimension. Thus, a complete proof of the
      a-theorem along the line of their argument in the most generic scenario would
      establish the equivalence between scale invariance and conformal invariance,
      which is another long-standing conjecture in four-dimensional quantum field
      theories.

      DOI: 10.1142/S0217732312500290

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      その他リンク: http://arxiv.org/pdf/1110.2586v2

    • Comments on scale invariant but non-conformal supersymmetric field theories

      Yu Nakayama

          2011年9月27日

      詳細を見る

      We investigate a possibility of scale invariant but non-conformal
      supersymmetric field theories from a perturbative approach. The explicit
      existence of monotonically decreasing a-function that generates beta-functions
      as a gradient flow provides a strong obstruction for such a possibility at
      two-loop order. We comment on the "discovery" of scale invariant but
      non-conformal renormalization group trajectories via a "change of scheme" in
      (4-\epsilon) dimension proposed in literatures.

      DOI: 10.1142/S0217751X12501229

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      その他リンク: http://arxiv.org/pdf/1109.5883v1

    • Gravity Dual for Cyclic Renormalization Group Flow without Conformal Invariance

      Yu Nakayama

          2011年7月14日

      詳細を見る

      We construct a gravity dual for scale invariant but non-conformal field
      theories with a cyclic renormalization group flow. A slight modification of our
      construction gives a gravity dual of discretely scale invariant field theories.
      The underlying gravitational theory breaks the null energy condition.

      DOI: 10.1142/S0217732311036930

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      その他リンク: http://arxiv.org/pdf/1107.2928v2

    • Comments on Worldsheet Description of the Omega Background

      Yu Nakayama, Hirosi Ooguri

          2011年6月27日

      詳細を見る

      Nekrasov's partition function is defined on a flat bundle of R^4 over S^1
      called the Omega background. When the fibration is self-dual, the partition
      function is known to be equal to the topological string partition function,
      which computes scattering amplitudes of self-dual gravitons and graviphotons in
      type II superstring compactified on a Calabi-Yau manifold. We propose a
      generalization of this correspondence when the fibration is not necessarily
      self-dual.

      DOI: 10.1142/S0217751X12501229

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      その他リンク: http://arxiv.org/pdf/1106.5503v1

    • 4D and 2D superconformal index with surface operator

      Yu Nakayama

          2011年5月24日

      詳細を見る

      We study the superconformal index of the N=4 super-Yang-Milles theory on S^3
      X S^1 with the half BPS superconformal surface operator (defect) inserted at
      the great circle of S^3. The half BPS superconformal surface operators preserve
      the same supersymmetry as well as the symmetry of the chemical potential used
      in the definition of the superconformal index, so the structure and the
      parameterization of the superconformal index remain unaffected by the presence
      of the surface operator. On the surface defect, a two-dimensional (4,4)
      superconformal field theory resides, and the four-dimensional superconformal
      index may be regarded as a superconformal index of the two-dimensional (4,4)
      superconformal field theory coupled with the four-dimensional bulk system. We
      construct the matrix model that computes the superconformal index with the
      surface operator when it couples with the bulk N=4 super-Yang-Milles theory
      through the defect hypermultiplets on it.

      DOI: 10.1007/JHEP08(2011)084

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      その他リンク: http://arxiv.org/pdf/1105.4883v3

    • What Maxwell Theory in D<>4 teaches us about scale and conformal invariance

      Sheer El-Showk, Yu Nakayama, Slava Rychkov

          2011年1月27日

      詳細を見る

      The free Maxwell theory in D<>4 dimensions provides a physical example of a
      unitary, scale invariant theory which is NOT conformally invariant. The easiest
      way to see this is that the field strength operator F_mn is neither a primary
      nor a descendant. We show how conformal multiplets can be completed, and
      conformality restored, by adding new local operators to the theory. In D>=5,
      this can only be done by sacrificing unitarity of the extended Hilbert space.
      We analyze the full symmetry structure of the extended theory, which turns out
      to be related to the OSp(D,2|2) superalgebra.

      DOI: 10.1016/j.nuclphysb.2011.03.008

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      その他リンク: http://arxiv.org/pdf/1101.5385v2

    • Higher derivative corrections in holographic Zamolodchikov-Polchinski theorem

      Yu Nakayama

          2010年9月2日

      詳細を見る

      We study higher derivative corrections in holographic dual of
      Zamolodchikov-Polchinski theorem that states the equivalence between scale
      invariance and conformal invariance in unitary d-dimensional Poincare invariant
      field theories. From the dual holographic perspective, we find that a
      sufficient condition to show the holographic theorem is the generalized strict
      null energy condition of the matter sector in effective (d+1)-dimensional
      gravitational theory. The same condition has appeared in the holographic dual
      of the "c-theorem" and our theorem suggests a deep connection between the two,
      which was manifested in two-dimensional field theoretic proof of the both.

      DOI: 10.1140/epjc/s10052-012-1870-z

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      その他リンク: http://arxiv.org/pdf/1009.0491v3

    • Refined topological amplitudes in N=1 flux compactification

      Yu Nakayama

          2010年9月2日

      詳細を見る

      We study the implication of refined topological string amplitudes in the
      supersymmetric N=1 flux compactification. They generate higher derivative
      couplings among the vector multiplets and graviphoton with generically
      non-holomorphic moduli dependence. For a particular term, we can compute them
      by assuming the geometric engineering. We claim that the Dijkgraaf-Vafa large N
      matrix model with the beta-ensemble measure directly computes the higher
      derivative corrections to the supersymmetric effective action of the
      supersymmetric N=1$ gauge theory.

      DOI: 10.1007/JHEP11(2010)117

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      その他リンク: http://arxiv.org/pdf/1009.0543v2

    • Eternal Inflation with Liouville Cosmology

      Yu Nakayama

          2010年7月30日

      詳細を見る

      We present a concrete holographic realization of the eternal inflation and
      its census taker in (1+1) dimensional Liouville gravity by applying the FRW/CFT
      philosophy proposed by Freivogel, Sekino, Susskind and Yeh (FSSY). The dual
      boundary theory is nothing but the old matrix model describing the
      two-dimensional Liouville gravity coupled with minimal model matter fields. In
      Liouville gravity, the flat Minkowski space or even the AdS space will decay
      into the dS space, which is in stark contrast with higher dimensional theories,
      but the spirit of the FSSY conjecture applies with only minimal modification.
      We investigate the classical geometry as well as some correlation functions to
      support our claim. We also study an analytic continuation to the time-like
      Liouville theory to discuss possible applications in (1+3) dimensional
      cosmology along with the original FSSY conjecture, where the boundary theory
      involves the time-like Liouville theory. We show that the decay rate in the
      (1+3) dimension is more suppressed due to the quantum gravity correction of the
      boundary theory.

      DOI: 10.1016/j.nuclphysb.2010.12.018

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      その他リンク: http://arxiv.org/pdf/1007.5499v2

    • Refined Cigar and Omega-deformed Conifold

      Yu Nakayama

          2010年4月17日

      詳細を見る

      Antoniadis et al proposed a relation between the Omega-deformation and
      refined correlation functions of the topological string theory. We investigate
      the proposal for the deformed conifold geometry from a non-compact Gepner model
      approach. The topological string theory on the deformed conifold has a dual
      description in terms of the c=1 non-critical string theory at the self-dual
      radius, and the Omega-deformation yields the radius deformation. We show that
      the refined correlation functions computed from the twisted SL(2,R)/U(1)
      Kazama-Suzuki coset model at level k=1 have direct c=1 non-critical string
      theory interpretations. After subtracting the leading singularity to procure
      the 1PI effective action, we obtain the agreement with the proposal.

      DOI: 10.1007/JHEP07(2010)054

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      その他リンク: http://arxiv.org/pdf/1004.2986v3

    • Gravity Dual for a Model of Perception

      Yu Nakayama

          2010年3月30日

      詳細を見る

      One of the salient features of human perception is its invariance under
      dilatation in addition to the Euclidean group, but its non-invariance under
      special conformal transformation. We investigate a holographic approach to the
      information processing in image discrimination with this feature. We claim that
      a strongly coupled analogue of the statistical model proposed by Bialek and Zee
      can be holographically realized in scale invariant but non-conformal Euclidean
      geometries. We identify the Bayesian probability distribution of our
      generalized Bialek-Zee model with the GKPW partition function of the dual
      gravitational system. We provide a concrete example of the geometric
      configuration based on a vector condensation model coupled with the Euclidean
      Einstein-Hilbert action. From the proposed geometry, we study sample
      correlation functions to compute the Bayesian probability distribution.

      DOI: 10.1016/j.aop.2010.09.009

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      その他リンク: http://arxiv.org/pdf/1003.5729v2

    • Universal time-dependent deformations of Schrodinger geometry

      Yu Nakayama

          2010年2月3日

      詳細を見る

      We investigate universal time-dependent exact deformations of Schrodinger
      geometry. We present 1) scale invariant but non-conformal deformation, 2)
      non-conformal but scale invariant deformation, and 3) both scale and conformal
      invariant deformation. All these solutions are universal in the sense that we
      could embed them in any supergravity constructions of the Schrodinger invariant
      geometry. We give a field theory interpretation of our time-dependent
      solutions. In particular, we argue that any time-dependent chemical potential
      can be treated exactly in our gravity dual approach.

      DOI: 10.1007/JHEP04(2010)102

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      その他リンク: http://arxiv.org/pdf/1002.0615v2

    • Schrödinger-like Dilaton Gravity

      Yu Nakayama

          2010年1月20日

      詳細を見る

      We investigate possibilities for a Schr\"odinger-like gravity with the
      dynamical critical exponent $z=2$, where the action only contains the
      first-order time derivative. The Horava gravity always admits such a relevant
      deformation because the full $(d+1)$ dimensional diffeomorphism of the Einstein
      gravity is replaced by the foliation preserving diffeomorphism. The dynamics is
      locally trivial or topological in the pure gravity case, but we can construct a
      dynamical field theory with a $z=2$ dispersion relation by introducing a
      dilaton degree of freedom. Our model provides a classical starting point for
      the possible quantum dilaton gravity which may be applied to a membrane
      quantization.

      DOI: 10.3842/SIGMA.2011.014

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      その他リンク: http://arxiv.org/pdf/1001.3436v3

    • Scale invariance vs conformal invariance from holography 査読有り

      Yu Nakayama

      Int.J.Mod.Phys.A   2010年

      詳細を見る

      記述言語:英語   掲載種別:研究論文(学術雑誌)  

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    • Anisotropic scale invariant cosmology

      Yu Nakayama

          2009年12月28日

      詳細を見る

      We study a possibility of anisotropic scale invariant cosmology. It is shown
      that within the conventional Einstein gravity, the violation of the null energy
      condition is necessary. We construct an example based on a ghost condensation
      model that violates the null energy condition. The cosmological solution
      necessarily contains at least one contracting spatial direction as in the
      Kasner solution. Our cosmology is conjectured to be dual to, if any, a
      non-unitary anisotropic scale invariant Euclidean field theory. We investigate
      simple correlation functions of the dual theory by using the holographic
      computation. After compactification of the contracting direction, our setup may
      yield a dual field theory description of the winding tachyon condensation that
      might solve the singularity of big bang/crunch of the universe.

      DOI: 10.1007/s10714-010-1083-4

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      その他リンク: http://arxiv.org/pdf/0912.5118v2

    • No Forbidden Landscape in String/M-theory

      Yu Nakayama

          2009年9月24日

      詳細を見る

      Scale invariant but non-conformal field theories are forbidden in (1+1)
      dimension, and so should be the corresponding holographic dual gravity
      theories. We conjecture that such scale invariant but non-conformal field
      configurations do not exist in the string/M-theory. We provide a proof of this
      conjecture in the classical supergravity limit under a certain gauge condition.
      Our proof does also apply in higher dimensional scale invariant but
      non-conformal field configurations, which suggests that scale invariant but
      non-conformal field theories may be forbidden in higher dimensions as well.

      DOI: 10.1007/JHEP01(2010)030

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      その他リンク: http://arxiv.org/pdf/0909.4297v3

    • Forbidden Landscape from Holography

      Yu Nakayama

          2009年7月1日

      詳細を見る

      We present a class of field configurations that are forbidden in the quantum
      gravity because of inconsistency in the dual field theory from holography.
      Scale invariant but non-conformal field theories are impossible in (1+1)
      dimension, and so should be the corresponding gravity dual. In particular, the
      "spontaneous Lorentz symmetry breaking" models and the "ghost condensation"
      models, which are well-studied in phenomenology literatures, are forbidden in
      any consistent quantum theories of gravity in (1+2) dimension since they
      predict such inconsistent field configurations.

      DOI: 10.1088/1126-6708/2009/11/061

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      その他リンク: http://arxiv.org/pdf/0907.0227v2

    • Gravity Dual for Reggeon Field Theory and Non-linear Quantum Finance

      Yu Nakayama

          2009年6月23日

      詳細を見る

      We study scale invariant but not necessarily conformal invariant deformations
      of non-relativistic conformal field theories from the dual gravity viewpoint.
      We present the corresponding metric that solves the Einstein equation coupled
      with a massive vector field. We find that, within the class of metric we study,
      when we assume the Galilean invariance, the scale invariant deformation always
      preserves the non-relativistic conformal invariance. We discuss applications to
      scaling regime of Reggeon field theory and non-linear quantum finance. These
      theories possess scale invariance but may or may not break the conformal
      invariance, depending on the underlying symmetry assumptions.

      DOI: 10.1142/S0217751X09047594

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      その他リンク: http://arxiv.org/pdf/0906.4112v1

    • On D3-brane Dynamics at Strong Warping

      Heng-Yu Chen, Yu Nakayama, Gary Shiu

          2009年5月27日

      詳細を見る

      We study the dynamics of a D3 brane in generic IIB warped compactifications,
      using the Hamiltonian formulation discussed in arXiv:0805.3700 [hep-th]. Taking
      into account of both closed and open string fluctuations, we derive the warped
      Kahler potential governing the motion of a probe D3 brane. By including the
      backreaction of D3, we also comment on how the problem of defining a
      holomorphic gauge coupling on wrapped D7 branes in warped background can be
      resolved.

      DOI: 10.1142/S0217751X10048366

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      その他リンク: http://arxiv.org/pdf/0905.4463v1

    • Observables and Correlators in Nonrelativistic ABJM Theory

      Yu Nakayama, Soo-Jong Rey

          2009年5月18日

      詳細を見る

      Non-relativistic ABJM theory is defined by Galilean limit of mass-deformed
      N=6 Chern-Simons theory. Holographic string theory dual to the theory is not
      known yet. To understand features candidate gravity dual might exhibit, we
      examine local and nonlocal physical observables and their correlations in the
      non-relativistic ABJM theory. We show that gauge invariant local observables
      correspond to zero-norm states and that correlation functions among them are
      trivial. We also show that a particular class of nonlocal observables, Wilson
      loops, are topological in the sense that their correlation functions coincide
      with those of pure Chern-Simons theory. We argue that the theory is
      nevertheless physical and illustrate several physical observables whose
      correlation functions are nontrivial. We also study quantum aspects. We show
      that Chern-Simons level is finitely renormalized and that dilatation operator
      acting on spin chain is trivial at planar limit. These results all point to
      string scale geometry of gravity dual and to intriguing topological and
      tensionless nature of dual string defined on it.

      DOI: 10.1088/1126-6708/2009/08/029

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      その他リンク: http://arxiv.org/pdf/0905.2940v2

    • Unparticles and Holographic Renormalization Group

      Chiu Man Ho, Yu Nakayama

          2009年3月3日

      詳細を見る

      We revisit the unparticle interactions and propagators from the AdS-CFT point
      of view, and we show how the contact terms and their renormalization group flow
      appear in the context of the holographic renormalization. We study both vector
      unparticles and unfermions, uncovering the relevant boundary conditions and
      renormalization group flows.

      DOI: 10.1088/1126-6708/2009/05/081

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      その他リンク: http://arxiv.org/pdf/0903.0420v3

    • Nambu-Goldstone Dark Matter and Cosmic Ray Electron and Positron Excess

      Masahiro Ibe, Yu Nakayama, Hitoshi Murayama, Tsutomu T. Yanagida

          2009年2月17日

      詳細を見る

      We propose a model of dark matter identified with a pseudo-Nambu-Goldstone
      boson in the dynamical supersymmetry breaking sector in a gauge mediation
      scenario. The dark matter particles annihilate via a below-threshold narrow
      resonance into a pair of R-axions each of which subsequently decays into a pair
      of light leptons. The Breit-Wigner enhancement explains the excess electron and
      positron fluxes reported in the recent cosmic ray experiments PAMELA, ATIC and
      PPB-BETS without postulating an overdensity in halo, and the limit on
      anti-proton flux from PAMELA is naturally evaded.

      DOI: 10.1088/1126-6708/2009/04/087

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      その他リンク: http://arxiv.org/pdf/0902.2914v1

    • Superfield Formulation for Non-Relativistic Chern-Simons-Matter Theory

      Yu Nakayama

          2009年2月13日

      詳細を見る

      We construct a superfield formulation for non-relativistic
      Chern-Simons-Matter theories with manifest dynamical supersymmetry. By
      eliminating all the auxiliary fields, we show that the simple action reduces to
      the one obtained by taking non-relativistic limit from the relativistic
      Chern-Simons-Matter theory proposed in the literature. As a further
      application, we give a manifestly supersymmetric derivation of the
      non-relativistic ABJM theory.

      DOI: 10.1007/s11005-009-0327-2

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      その他リンク: http://arxiv.org/pdf/0902.2267v1

    • Non-Relativistic M2-brane Gauge Theory and New Superconformal Algebra

      Yu Nakayama, Makoto Sakaguchi, Kentaroh Yoshida

          2009年2月12日

      詳細を見る

      We study non-relativistic limits of the N=6 Chern-Simons-Matter theory that
      arises as a low-energy limit of the M2-brane gauge theory with background flux.
      The model admits several different non-relativistic limits and we find that the
      maximal supersymmetry we construct has 14 components of supercharges, which is
      a novel example of non-relativistic superconformal algebra in (1+2) dimension.
      We also investigate the other limits that realize less supersymmetries.

      DOI: 10.1088/1126-6708/2009/04/096

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      その他リンク: http://arxiv.org/pdf/0902.2204v2

    • Conformal Gauge Mediation and Light Gravitino of Mass m(3/2) < O(10) eV 査読有り

      Masahiro Ibe, Yu Nakayama, Tsutomu Yanagida

      Phys.Lett.B   2009年

      詳細を見る

      記述言語:英語   掲載種別:研究論文(学術雑誌)  

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    • Emerging AdS from Extremally Rotating NS5-branes

      Yu Nakayama

          2008年12月11日

      詳細を見る

      We investigate the near-horizon limit of extremally rotating NS5-branes. The
      resulting geometry has SL(2,R) \times U(1)^2 isometry. The asymptotic symmetry
      group contains a chiral Virasoro algebra, and we obtain two different
      realizations depending on the boundary conditions we impose. When one of the
      two angular momenta vanishes, the symmetry is enhanced to AdS_3. The entropy of
      the boundary theory can be estimated from the Cardy formula and it agrees with
      the Bekenstein-Hawking entropy of the bulk theory. We can embed the extremally
      rotating NS5-brane geometry in an exactly solvable string background, which may
      yield microscopic understanding of this duality, especially about the
      mysterious enhancement of the symmetry from AdS_2 to AdS_3. The construction
      suggests emerging Virasoro symmetries in the extreme corner of the (1+5)
      dimensional little string theory.

      DOI: 10.1016/j.physletb.2009.02.031

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      その他リンク: http://arxiv.org/pdf/0812.2234v3

    • Interacting SUSY-singlet matter in non-relativistic Chern-Simons theory

      Yu Nakayama, Makoto Sakaguchi, Kentaroh Yoshida

          2008年12月8日

      詳細を見る

      We construct an example of supersymmetric Chern-Simons-matter theory with a
      matter field transforming as a singlet representation of the supersymmetry
      algebra, where the bosonic and fermionic degrees of freedom do not match. This
      is obtained as a non-relativistic limit of the N=2 Chern-Simons-matter theory
      in 1+2 dimensions, where the particle and anti-particle coexist. We also study
      the index to investigate the mimatch of bosonic and fermionic degrees of
      freedom.

      DOI: 10.1088/1751-8113/42/19/195402

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      その他リンク: http://arxiv.org/pdf/0812.1564v1

    • A family of super Schrodinger invariant Chern-Simons matter systems

      Yu Nakayama, Shinsei Ryu, Makoto Sakaguchi, Kentaroh Yoshida

          2008年11月15日

      詳細を見る

      We investigate non-relativistic limits of the N=3 Chern-Simons matter system
      in 1+2 dimensions. The relativistic theory can generate several inequivalent
      super Schodinger invariant theories, depending on the degrees of freedom we
      choose to retain in the non-relativistic limit. The maximally supersymmetric
      Schrodinger invariant theory is obtained by keeping all particle degrees of
      freedom. The other descendants, where particles and anti-particles coexist, are
      also Schrodinger invariant but preserve less supersymmetries. Thus, we have a
      family of super Schrodinger invariant field theories produced from the parent
      relativistic theory.

      DOI: 10.1088/1126-6708/2009/01/006

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      その他リンク: http://arxiv.org/pdf/0811.2461v2

    • Non-compact Mirror Bundles and (0,2) Liouville Theories

      Yu Nakayama

          2008年10月22日

      詳細を見る

      We study (0,2) deformations of N=2 Liouville field theory and its mirror
      duality. A gauged linear sigma model construction of the ultraviolet theory
      connects (0,2) deformations of Liouville field theory and (0,2) deformations of
      N=2 SL(2,R)/U(1) coset model as a mirror duality. Our duality proposal from the
      gauged linear sigma model completely agrees with the exact CFT analysis. In the
      context of heterotic string compactifications, the deformation corresponds to
      the introduction of a non-trivial gauge bundle. This non-compact
      Landau-Ginzburg construction yields a novel way to study the gauge bundle
      moduli for non-compact Calabi-Yau manifolds.

      DOI: 10.1088/1126-6708/2009/03/062

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      その他リンク: http://arxiv.org/pdf/0810.4160v1

    • An Index for Non-relativistic Superconformal Field Theories

      Yu Nakayama

          2008年7月21日

      詳細を見る

      We study the highest-weight representation of N=2 supersymmetric Schrodinger
      algebra which appears in non-relativistic superconformal field theories in
      (1+2) dimension. We define the index for the non-relativistic superconformal
      field theories and study its properties. As a concrete example, we compute the
      index for the non-relativistic limit of N=6 superconformal Chern-Simons-matter
      theory recently proposed by Aharony et al.

      DOI: 10.1088/1126-6708/2008/10/083

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      その他リンク: http://arxiv.org/pdf/0807.3344v5

    • Langlands duality in Liouville-H_3^+ WZNW correspondence

      Gaston Giribet, Yu Nakayama, Lorena Nicolas

          2008年5月9日

      詳細を見る

      We show a physical realization of the Langlands duality in correlation
      functions of H_3^+ WZNW model. We derive a dual version of the
      Stoyanovky-Riabult-Teschner (SRT) formula that relates the correlation function
      of the H_3^+ WZNW and the dual Liouville theory to investigate the level
      duality k-2 \to (k-2)^{-1} in the WZNW correlation functions. Then, we show
      that such a dual version of the H_3^+ - Liouville relation can be interpreted
      as a particular case of a biparametric family of non-rational CFTs based on the
      Liouville correlation functions, which was recently proposed by Ribault. We
      study symmetries of these new non-rational CFTs and compute correlation
      functions explicitly by using the free field realization to see how a
      generalized Langlands duality manifests itself in this framework. Finally, we
      suggest an interpretation of the SRT formula as realizing the Drinfeld-Sokolov
      Hamiltonian reduction. Again, the Hamiltonian reduction reveals the Langlands
      duality in the H_3^+ WZNW model. Our new identity for the correlation functions
      of H_3^+ WZNW model may yield a first step to understand quantum geometric
      Langlands correspondence yet to be formulated mathematically.

      DOI: 10.1142/S0217751X09044607

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      その他リンク: http://arxiv.org/pdf/0805.1254v1

    • Dangerous Liouville Wave -- exactly marginal but non-conformal deformation

      Chiu Man Ho, Yu Nakayama

          2008年4月23日

      詳細を見る

      We give a non-trivially interacting field theory example of scale invariant
      but non-conformal field theory. The model is based on the exactly solvable
      Liouville field theory coupled with free scalars deformed by an exactly
      marginal operator. We show non-vanishing of the trace of the energy-momentum
      tensor by using the quantum Schwinger-Dyson equation for the Liouville field
      theory, which is a sophistication of the quantum higher equations of motion for
      the Liouville field theory introduced by Alyosha Zamolodchikov. Possibly
      dangerous implications for the super-critical string theory will be discussed.

      DOI: 10.1088/1126-6708/2008/07/109

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      その他リンク: http://arxiv.org/pdf/0804.3635v3

    • Conformal Supersymmetry Breaking and Dynamical Tuning of the Cosmological Constant 査読有り

      Masahiro Ibe, Yu Nakayama, Tsutomu Yanagida

      Phys.Lett.B   2008年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

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    • Stable SUSY Breaking Model with O(10) eV Gravitino from Combined D-term Gauge Mediation and U(1)' Mediation

      Yu Nakayama

          2007年12月4日

      詳細を見る

      We show a calculable example of stable supersymmetry (SUSY) breaking models
      with O(10) eV gravitino mass based on the combination of D-term gauge mediation
      and U(1)' mediation. A potential problem of the negative mass squared for the
      SUSY standard model (SSM) sfermions in the D-term gauge mediation is solved by
      the contribution from the U(1)' mediation. On the other hand, the splitting
      between the SSM gauginos and sfermions in the U(1)' mediation is circumvented
      by the contributions from the D-term gauge mediation. Since the U(1)' mediation
      does not introduce any new SUSY vacua, we achieve a completely stable model
      under thermal effects. Our model, therefore, has no cosmological difficulty.

      DOI: 10.1088/1126-6708/2008/02/013

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      その他リンク: http://arxiv.org/pdf/0712.0619v2

    • Moduli Stabilization in Stringy ISS Models

      Yu Nakayama, Masahito Yamazaki, T. T. Yanagida

          2007年9月28日

      詳細を見る

      We present a stringy realization of the ISS metastable SUSY breaking model
      with moduli stabilization. The mass moduli of the ISS model is stabilized by
      gauging of a U(1) symmetry and its D-term potential. The SUSY is broken both by
      F-terms and D-terms. It is possible to obtain de-Sitter vacua with a
      vanishingly small cosmological constant by an appropriate fine-tuning of flux
      parameters.

      DOI: 10.1016/j.physletb.2008.03.074

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      その他リンク: http://arxiv.org/pdf/0710.0001v3

    • SUSY Unparticle and Conformal Sequestering

      Yu Nakayama

          2007年7月17日

      詳細を見る

      We investigate unparticle physics with supersymmetry (SUSY). The SUSY
      breaking effects due to the gravity mediation induce soft masses for the SUSY
      unparticles and hence break the conformal invariance. The unparticle physics
      observable in near future experiments is only consistent if the SUSY breaking
      effects from the hidden sector to the standard model sector are dominated by
      the gauge mediation, or if the SUSY breaking effects to the unparticle sector
      is sufficiently sequestered. We argue that the natural realization of the
      latter possibility is the conformal sequestering scenario.

      DOI: 10.1103/PhysRevD.76.105009

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      その他リンク: http://arxiv.org/pdf/0707.2451v2

    • D-dualized D-brane

      Yu Nakayama

          2007年6月6日

      詳細を見る

      We further investigate the dimensional duality (D-duality) proposed in
      arXiv:0705.0550 by mainly focusing on the properties of D-branes in this
      background. We derive the world-sheet correspondence of static D-branes, and
      discuss the fate of non-static D-branes from the world-sheet viewpoint. The
      quantum string production with or without D-branes is also studied from the
      time-like Liouville theory. We find that the closed string production from the
      background is much larger than that from D-branes decaying into nothing.

      DOI: 10.1088/1126-6708/2007/08/085

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      その他リンク: http://arxiv.org/pdf/0706.0782v3

    • Gauge Mediation with D-term SUSY Breaking

      Y. Nakayama, Masato Taki, Taizan Watari, T. T. Yanagida

          2007年5月7日

      詳細を見る

      We construct a gauge-mediation model with a D-term supersymmetry (SUSY)
      breaking. R-symmetry breaking necessary for generating the SUSY standard-model
      gaugino masses is given by gaugino condensation of a strongly coupled gauge
      theory in the hidden sector. The energy scale of the strong dynamics of the
      hidden sector gauge theory should be around the messenger mass scale M, or
      otherwise perturbative calculations would be reliable and would lead to
      negative soft mass squared for squarks and sleptons. Thus, all the mass scales
      are controlled by a virtually single parameter, \sqrt{D}/M. This model covers a
      very wide range of gravitino mass, m_{3/2} \simeq 1 eV--100 TeV. Possible
      embeddings of the model in string theory are also discussed.

      DOI: 10.1016/j.physletb.2007.08.064

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      その他リンク: http://arxiv.org/pdf/0705.0865v2

    • Conformal Gauge Mediation

      M. Ibe, Y. Nakayama, T. T. Yanagida

          2007年3月10日

      詳細を見る

      We propose a one-parameter theory for gauge mediation of supersymmetry (SUSY)
      breaking. The spectrum of SUSY particles such as squarks and sleptons in the
      SUSY standard-model and the dynamics of SUSY-breaking sector are, in principle,
      determined only by one parameter in the theory, that is, the mass of
      messengers. Above the messenger threshold all gauge coupling and Yukawa
      coupling constants in the SUSY-breaking sector are on the infrared fixed point.
      We find that the present theory may predict a split spectrum of the
      standard-model SUSY particles, m_{gaugino} < m_{sfermion}, where m_{gaugino}
      and m_{sfermion} are SUSY-breaking masses for gauginos and squarks/sleptons,
      respectively.

      DOI: 10.1016/j.physletb.2007.04.002

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      その他リンク: http://arxiv.org/pdf/hep-ph/0703110v1

    • Black Hole - String Transition and Rolling D-brane

      Yu Nakayama

          2007年2月28日

      詳細を見る

      We investigate the black hole - string transition in the two-dimensional
      Lorentzian black hole system from the exact boundary states that describe the
      rolling D-brane falling down into the two-dimensional black hole. The black
      hole - string phase transition is one of the fundamental properties of the
      non-supersymmetric black holes in string theory, and we will reveal the nature
      of the phase transition from the exactly solvable world-sheet conformal field
      theory viewpoint. Since the two-dimensional Lorentzian black hole system
      (SL(2;R)_k/U(1) coset model at level k) typically appears as near-horizon
      geometries of various singularities such as NS5-branes in string theory, our
      results can be regarded as the probe of such singularities from the
      non-supersymmetric probe rolling D-brane. The exact construction of boundary
      states for the rolling D0-brane falling down into the two-dimensional D-brane
      enables us to probe the phase transition at k=1 directly in the physical
      amplitudes. During the study, we uncover three fundamental questions in string
      theory as a consistent theory of quantum gravity: small charge limit v.s. large
      charge limit of non-supersymmetric quantum black holes, analyticity v.s.
      non-analyticity in physical amplitudes and physical observables, and unitarity
      v.s. open closed duality in time-dependent string backgrounds. This work is
      based on the PhD thesis submitted to Department of Physics, Faculty of Science,
      University of Tokyo, which was defended on January 2007.

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      その他リンク: http://arxiv.org/pdf/hep-th/0702221v2

    • Finite N Index and Angular Momentum Bound from Gravity

      Yu Nakayama

          2007年1月23日

      詳細を見る

      We exactly compute the finite N index and BPS partition functions for N=4 SYM
      theory in a newly proposed maximal angular momentum limit. The new limit is not
      predicted from the superconformal algebra, but naturally arises from the
      supergravity dual. We show that the index does not receive any finite N
      corrections while the free BPS partition function does.

      DOI: 10.1007/s10714-007-0480-9

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      その他リンク: http://arxiv.org/pdf/hep-th/0701208v2

    • The Nothing at the Beginning of the Universe Made Precise

      Yu Nakayama, Soo-Jong Rey, Yuji Sugawara

          2006年6月14日

      詳細を見る

      We propose a new worldsheet approach to the McGreevy-Silverstein proposal:
      resolution of spacelike singularity via Scherk-Schwarz compactification and
      winding string condensation therein. Our proposal is built upon so-called three
      parameter sine-Liouville theory, which has useful features and could be
      solvable in conformal field theory method. Utilizing standard Wick rotation, we
      compute string pair production rate exactly in terms of renormalized worldsheet
      cosmological constant and find that the production rate is finite for six or
      less spacetime dimensions. We also find that the sine-Liouville potential
      excises string excitation in the asymptotic past, and that such "Nothing state"
      is realizable for a range of sine-Liouville coupling constants. We compute one
      loop vacuum-to-vacuum transition amplitude and again detect presence of the
      "Nothing state". We also survey various worldsheet approaches to the tachyon
      condensation based on timelike Liouville theory. We point out that string
      theory on a conifold provides the upper critical dimension for realizing the
      "Nothing state", thus making contact with the blackhole / string transition
      point.

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      その他リンク: http://arxiv.org/pdf/hep-th/0606127v1

    • Unitarity Meets Channel-Duality for Rolling / Decaying D-Branes

      Yu Nakayama, Soo-Jong Rey, Yuji Sugawara

          2006年5月1日

      詳細を見る

      Investigations for decay of unstable D-brane and rolling of accelerated
      D-brane dynamics have revealed that various proposed prescriptions give
      different result for spectral amplitudes and observables. Here, we study them
      with particular attention to unitarity and open-closed channel duality. From
      "ab initio" derivation in the open string channel, both in Euclidean and
      Lorentzian worldsheet approaches, we find heretofore overlooked contribution to
      the spectral amplitudes and obervables. The contribution is fortuitously absent
      for decay of unstable D-brane, but is present for rolling of accelerated
      D-brane. We finally show that the contribution is imperative for ensuring
      unitarity and optical theorem at each order in string loop expansion.

      DOI: 10.1088/1126-6708/2006/08/014

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      その他リンク: http://arxiv.org/pdf/hep-th/0605013v1

    • Index for Supergravity on AdS_5 \times T^{1,1} and Conifold Gauge Theory

      Yu Nakayama

          2006年2月28日

      詳細を見る

      We compute the index for the conifold gauge theory from type IIB supergravity
      (superstring) on AdS_5 \times T^{1,1}. We discuss its implication from the
      gauge theory viewpoint.

      DOI: 10.1016/j.nuclphysb.2006.08.012

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      その他リンク: http://arxiv.org/pdf/hep-th/0602284v2

    • Index for Orbifold Quiver Gauge Theories

      Yu Nakayama

          2005年12月22日

      詳細を見る

      We compute the index for orbifold quiver gauge theories. We compare it with
      the results obtained from the type IIB supergravity (superstring) on AdS_5
      \times S^5/\Gamma.

      DOI: 10.1016/j.physletb.2006.03.045

      researchmap

      その他リンク: http://arxiv.org/pdf/hep-th/0512280v3

    • More on Conformally Sequestered SUSY Breaking

      M. Ibe, K. -I. Izawa, Yu Nakayama, Y. Shinbara, T. Yanagida

          2005年9月22日

      詳細を見る

      We extend our models for conformal sequestering of dynamical supersymmetry
      breaking with decoupling vector-like matter in several different ways. These
      extensions enable us to simplify concrete model building, in particular,
      rendering large gauge group and ad hoc global symmetry for sequestering
      unnecessary. Conformal sequestering appears highly natural in such
      circumstances.

      DOI: 10.1103/PhysRevD.73.035012

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      その他リンク: http://arxiv.org/pdf/hep-ph/0509229v2

    • D-Brane Propagation in Two-Dimensional Black Hole Geometries

      Yu Nakayama, Soo-Jong Rey, Yuji Sugawara

          2005年7月5日

      詳細を見る

      We study propagation of D0-brane in two-dimensional Lorentzian black hole
      backgrounds by the method of boundary conformal field theory of SL(2,R)/U(1)
      supercoset at level k. Typically, such backgrounds arise as near-horizon
      geometries of k coincident non-extremal NS5-branes, where 1/k measures
      curvature of the backgrounds in string unit and hence size of string worldsheet
      effects. At classical level, string worldsheet effects are suppressed and
      D0-brane propagation in the Lorentzian black hole geometry is simply given by
      the Wick rotation of D1-brane contour in the Euclidean black hole geometry.
      Taking account of string worldsheet effects, boundary state of the Lorentzian
      D0-brane is formally constructible via Wick rotation from that of the Euclidean
      D1-brane. However, the construction is subject to ambiguities in boundary
      conditions. We propose exact boundary states describing the D0-brane, and
      clarify physical interpretations of various boundary states constructed from
      different boundary conditions. As it falls into the black hole, the D0-brane
      radiates off to the horizon and to the infinity. From the boundary states
      constructed, we compute physical observables of such radiative process. We find
      that part of the radiation to infinity is in effective thermal distribution at
      the Hawking temperature. We also find that part of the radiation to horizon is
      in the Hagedorn distribution, dominated by massive, highly non-relativistic
      closed string states, much like the tachyon matter. Remarkably, such
      distribution emerges only after string worldsheet effects are taken exactly
      into account. From these results, we observe that nature of the radiation
      distribution changes dramatically across the conifold geometry k=1 (k=3 for the
      bosonic case), exposing the `string - black hole transition' therein.

      DOI: 10.1088/1126-6708/2005/09/020

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      その他リンク: http://arxiv.org/pdf/hep-th/0507040v2

    • Conformally Sequestered SUSY Breaking in Vector-like Gauge Theories

      M. Ibe, K. -I. Izawa, Yu Nakayama, Y. Shinbara, T. Yanagida

          2005年6月3日

      詳細を見る

      We provide, in a framework of vector-like gauge theories, concrete models for
      conformal sequestering of dynamical supersymmetry (SUSY) breaking in the hidden
      sector. If the sequestering is sufficiently strong, anomaly mediation of the
      SUSY breaking may give dominant contributions to the mass spectrum of SUSY
      standard-model particles, leading to negative slepton masses squared. Thus, we
      also consider a model with gravitational gauge mediation to circumvent the
      tachyonic slepton problem in pure anomaly mediation models.

      DOI: 10.1103/PhysRevD.73.015004

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      その他リンク: http://arxiv.org/pdf/hep-ph/0506023v2

    • The Stoyanovsky-Ribault-Teschner Map and String Scattering Amplitudes

      Gaston Giribet, Yu Nakayama

          2005年5月23日

      詳細を見る

      Recently, Ribault and Teschner pointed out the existence of a one-to-one
      correspondence between N-point correlation functions for the SL(2,C)_k/SU(2)
      WZNW model on the sphere and certain set of 2N-2-point correlation functions in
      Liouville field theory. This result is based on a seminal work by Stoyanovsky.
      Here, we discuss the implications of this correspondence focusing on its
      application to string theory on curved backgrounds. For instance, we analyze
      how the divergences corresponding to worldsheet instantons in AdS_3 can be
      understood as arising from the insertion of the dual screening operator in the
      Liouville theory side. We also study the pole structure of N-point functions in
      the 2D Euclidean black hole and its holographic meaning in terms of the Little
      String Theory. This enables us to interpret the correspondence between CFTs as
      encoding a LSZ-type reduction procedure. Furthermore, we discuss the scattering
      amplitudes violating the winding number conservation in those backgrounds and
      provide a formula connecting such amplitudes with observables in Liouville
      field theory. Finally, we study the WZNW correlation functions in the limit k
      -> 0 and show that, at the point k=0, the Stoyanovsky-Ribault-Teschner
      dictionary turns out to be in agreement with the FZZ conjecture at a particular
      point of the space of parameters where the Liouville central charge becomes
      c=-2. This result makes contact with recent studies on the dynamical tachyon
      condensation in closed string theory.

      DOI: 10.1142/S0217751X06031697

      researchmap

      その他リンク: http://arxiv.org/pdf/hep-th/0505203v1

    • Rolling Down the Throat in NS5-brane Background: The Case of Electrified D-Brane

      Yu Nakayama, Kamal L. Panigrahi, Soo-Jong Rey, Hiromitsu Takayanagi

          2004年12月5日

      詳細を見る

      We study rolling radion dynamics of electrified D-brane in NS5-brane
      background, both in effective field theory and in full open string theory. We
      construct exact boundary states and, from them, extract conserved Noether
      currents. We argue that T-duality and Lorentz boost offer an intuitive
      approach. In the limit of large number of NS5-branes, both boundary wave
      functions and conserved currents are sharply peaked and agree with those
      deduced from the effective field theory. As the number of NS5-branes is
      reduced, width around the peak becomes wider by string corrections. We also
      study radiative decay process. By applying Lorentz covariance, we show how the
      decay of electrified D-brane is related to that of bare D-brane. We compute
      spectral moments of final state energy and winding quantum number. Using
      Lorentz covariance argument, we explain in elementary way why winding quantum
      number should be included and derive rules how to do so. We conclude that
      Kutasov's "geometric realization" between radion rolling dynamics and tachyon
      rolling dynamics holds universally, both for bare and electrified D-branes.

      DOI: 10.1088/1126-6708/2005/01/052

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      その他リンク: http://arxiv.org/pdf/hep-th/0412038v2

    • Zamolodchikov relations and Liouville hierarchy in SL(2,R)_k WZNW model

      Gaetano Bertoldi, Stefano Bolognesi, Gaston Giribet, Marco Matone, Yu Nakayama

          2004年9月22日

      詳細を見る

      We study the connection between Zamolodchikov operator-valued relations in
      Liouville field theory and in the SL(2,R)_k WZNW model. In particular, the
      classical relations in SL(2,R)_k can be formulated as a classical Liouville
      hierarchy in terms of the isotopic coordinates, and their covariance is easily
      understood in the framework of the AdS_3/CFT_2 correspondence. Conversely, we
      find a closed expression for the classical Liouville decoupling operators in
      terms of the so called uniformizing Schwarzian operators and show that the
      associated uniformizing parameter plays the same role as the isotopic
      coordinates in SL(2,R)_k. The solutions of the j-th classical decoupling
      equation in the WZNW model span a spin j reducible representation of SL(2,R).
      Likewise, we show that in Liouville theory solutions of the classical
      decoupling equations span spin j representations of SL(2,R), which is
      interpreted as the isometry group of the hyperbolic upper half-plane. We also
      discuss the connection with the Hamiltonian reduction of SL(2,R)_k WZNW model
      to Liouville theory.

      DOI: 10.1016/j.nuclphysb.2005.01.001

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      その他リンク: http://arxiv.org/pdf/hep-th/0409227v1

    • Crosscap states in N=2 Liouville theory

      Yu Nakayama

          2004年9月3日

      詳細を見る

      We construct crosscap states in the N = 2 Liouville theory from the modular
      bootstrap method. We verify our results by comparing it with the calculation
      from the minisuperspace approximation and by checking the consistency with the
      conformal bootstrap equation. Various overlaps with other known branes are
      studied. We further discuss the topological nature of the discrete terms in the
      crosscap wavefunction and their connection with the Landau-Ginzburg approach in
      a nontrivial dilaton background. We find that it can be mapped to the
      Landau-Ginzburg theory with a negative power superpotential by a simple change
      of variables, extending the known duality to the open string sector. Possible
      applications to the two-dimensional noncritical string theories and
      supersymmetric orientifolds in the higher dimension are also discussed.

      DOI: 10.1016/j.nuclphysb.2004.11.064

      researchmap

      その他リンク: http://arxiv.org/pdf/hep-th/0409039v4

    • Boundary States for the Rolling D-branes in NS5 Background

      Yu Nakayama, Yuji Sugawara, Hiromitsu Takayanagi

          2004年6月21日

      詳細を見る

      In this paper we construct the time dependent boundary states describing the
      ``rolling D-brane solutions'' in the NS5 background discovered recently by
      Kutasov by means of the classical DBI analysis. We first survey some aspects of
      non-compact branes in the NS5 background based on known boundary states in the
      N=2 Liouville theory. We consider two types of non-compact branes, one of which
      is BPS and the other is non-BPS but stable. Then we clarify how to Wick-rotate
      the non-BPS one appropriately. We show that the Wick-rotated boundary state
      realizes the correct trajectory of rolling D-brane in the classical limit, and
      leads to well behaved spectral densities of open strings due to the existence
      of non-trivial damping factors of energy. We further study the cylinder
      amplitudes and the emission rates of massive closed string modes.

      DOI: 10.1088/1126-6708/2004/07/020

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      その他リンク: http://arxiv.org/pdf/hep-th/0406173v3

    • The Liouville Geometry of N=2 Instantons and the Moduli of Punctured Spheres

      Gaetano Bertoldi, Stefano Bolognesi, Marco Matone, Luca Mazzucato, Yu Nakayama

          2004年5月12日

      詳細を見る

      We study the instanton contributions of N=2 supersymmetric gauge theory and
      propose that the instanton moduli space is mapped to the moduli space of
      punctured spheres. Due to the recursive structure of the boundary in the
      Deligne-Knudsen-Mumford stable compactification, this leads to a new recursion
      relation for the instanton coefficients, which is bilinear. Instanton
      contributions are expressed as integrals on M_{0,n} in the framework of the
      Liouville F-models. This also suggests considering instanton contributions as a
      kind of Hurwitz numbers and also provides a prediction on the asymptotic form
      of the Gromov-Witten invariants.
      We also interpret this map in terms of the geometric engineering approach to
      the gauge theory, namely the topological A-model, as well as in the noncritical
      string theory framework. We speculate on the extension to nontrivial
      gravitational background and its relation to the uniformization program.
      Finally we point out an intriguing analogy with the self-dual YM equations for
      the gravitational version of SU(2) where surprisingly the same Hauptmodule of
      the SW solution appears.

      DOI: 10.1088/1126-6708/2004/05/075

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      その他リンク: http://arxiv.org/pdf/hep-th/0405117v3

    • Liouville Field Theory -- A decade after the revolution

      Yu Nakayama

          2004年2月2日

      詳細を見る

      We review recent developments (up to January 2004) of the Liouville field
      theory and its matrix model dual. This review consists of three parts. In part
      I, we review the bosonic Liouville theory. After briefly reviewing the
      necessary background, we discuss the bulk structure constants (the DOZZ
      formula) and the boundary states (the FZZT brane and the ZZ brane). Various
      applications are also presented. In part II, we review the supersymmetric
      extension of the Liouville theory. We first discuss the bulk structure
      constants and the branes as in the bosonic Liouville theory, and then we
      present the matrix dual descriptions with some applications. In part III, the
      Liouville theory on unoriented surfaces is reviewed. After introducing the
      crosscap state, we discuss the matrix model dual description and the tadpole
      cancellation condition. This review also includes some original material such
      as the derivation of the conjectured dual action for the N = 2 Liouville theory
      from other known dualities and the comparison of the Liouville crosscap state
      with the c = 0 unoriented matrix model. This is based on my master's thesis
      submitted to Department of Physics, Faculty of Science, University of Tokyo on
      January 2004.

      DOI: 10.1142/S0217751X04019500

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      その他リンク: http://arxiv.org/pdf/hep-th/0402009v7

    • Tadpole Cancellation in Unoriented Liouville Theory

      Yu Nakayama

          2003年9月5日

      詳細を見る

      The tadpole cancellation in the unoriented Liouville theory is discussed.
      Using two different methods -- the free field method and the boundary-crosscap
      state method, we derive one-loop divergences. Both methods require two
      D1-branes with the symplectic gauge group to cancel the orientifold tadpole
      divergence. However, the finite part left is different in each method and this
      difference is studied. We also discuss the validity of the free field method
      and the possible applications of our result.

      DOI: 10.1088/1126-6708/2003/11/017

      researchmap

      その他リンク: http://arxiv.org/pdf/hep-th/0309063v4

    • Effective Gauge Degrees of Freedom and the (Non)existence of the Glueball Superpotential

      Yu Nakayama

          2003年6月2日

      詳細を見る

      We propose an efficient way to obtain a correct Veneziano-Yankielowicz type
      integration constant of the effective glueball superpotential
      $W_{eff}(S,g,\Lambda)$, even for massless theories. Applying our method, we
      show some $\mathcal{N} = 1$ theories do not have such an effective glueball
      superpotential, even though they have isolated vacua. In these cases, $S = 0$
      typically.

      DOI: 10.1088/1126-6708/2003/08/049

      researchmap

      その他リンク: http://arxiv.org/pdf/hep-th/0306007v3

    ▼全件表示

    MISC

    • CP-violating supersymmetry anomaly

      Koichiro Nakagawa, Yu Nakayama

          2021年3月18日

      詳細を見る

      We show that CP-violating Weyl anomaly induces a supersymmetry anomaly in the
      formulation of superconformal supergravity as is observed in CP-preserving
      cases. This supersymmetry anomaly can be removed in the old minimal
      supergravity by adding suitable local counterterms, and it becomes a consistent
      theory.

      researchmap

      その他リンク: http://arxiv.org/pdf/2103.10048v1

    • On the trace anomaly of Chaudhuri-Choi-Rabinovici model

      Yu Nakayama

          2021年1月8日

      詳細を見る

      Recently a non-supersymmetric conformal field theory with an exactly marginal
      deformation in the large $N$ limit was constructed by
      Chaudhuri-Choi-Rabinovici. On a non-supersymmetric conformal manifold, $c$
      coefficient of the trace anomaly in four dimensions would generically change.
      In this model, we, however, find that it does not change at the first
      non-trivial order given by three-loop diagrams.

      researchmap

      その他リンク: http://arxiv.org/pdf/2101.02861v1

    書籍等出版物

    • 高次元共形場理論への招待―3次元臨界Ising模型を解く

      中山 優( 担当: 単著)

      サイエンス社  2019年11月1日 

      詳細を見る

      記述言語:日本語 著書種別:学術書

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    共同研究・競争的資金等の研究

    • 共形ブートストラップ

      その他の研究制度 

      詳細を見る

      2014年4月 - 現在

      資金種別:競争的資金

      researchmap

    • 共形ブートストラップで解く量子色力学のカイラル相転移現象

      日本学術振興会  科学研究費助成事業 若手研究(B) 

      中山 優

      詳細を見る

      2017年4月 - 2021年3月

      課題番号:17K14301

      配分額:4160000円 ( 直接経費:3200000円 、 間接経費:960000円 )

      本研究の眼目は共形対称性を元にしてQCDのカイラル相転移などの物理的に重要な相転移の性質を求めることである。本年度は、次の3点に注目して研究した。1.共形対称性を持った場の理論の性質を深く理解する。2.QCDのカイラル相転移が持つ対称性の性質を理論的に理解する。3.QCDの相転移に対して共形ブートストラップを適用することを考える。
      1の点については、射影空間上での共形場理論の性質や、あるいはポワンカレ対称性がないような場の量子論においての共形対称性の定義やその性質など、新しい場の理論の知見を得ることに成功した。また、共形場理論に現れるアノマリーに新しい性質のものが存在するのではないか?という観点からの研究もはじめている。
      2の点に関しては、格子シミュレーションの専門家と共同で、QCDのカイラル対称性が過去に考えられていたSU(2)の対称性の回復に伴って、アノマリーで破れていたU(1)対称性も回復するのではないか?という知見を得て、それが共形場理論に対してどのように影響を与えるのか調べた。また、QCDの拡張としてフレーバーの数を増やしていった時にどのような性質の共形場理論が現れるのか、あるいは、高次元で同じようなことが起こるのかと言う観点からも数値的な理解を進めた。
      3は現在進行中であり、既存の方法だけではなく新しいアイディアを取り入れてQCDの相転移の性質、とりわけ、その次数や臨界指数などを明らかにしていきたいと考えている。

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    • ブラックホール・ストリング相転移に基づいた量子重力とタキオン凝縮の物理

      日本学術振興会  科学研究費助成事業 特別研究員奨励費 

      中山 優

      詳細を見る

      2007年 - 2009年

      課題番号:07J01841

      配分額:1200000円 ( 直接経費:1200000円 )

      1、超対称共形場理論の素粒子現象への応用。
      超対称性を持つ素粒子標準模型の拡張において、1eV程度の軽いグラヴィティーノを予言する模型の構築は現象論的に大きな意義を持つ。申請者は、超共形場理論を基礎においた、新しいクラスのゲージ的伝達機構を提案し、軽いグラヴィティーノを実現する模型を、実際に構築した。
      2、4次元超共形代数の指数の研究。
      4次元共形場理論の分類において、指数の計はもっと基礎的で重要である。申請者は、Lare N極限を超えて、有限のゲージ群のランクでも指数が具体的に計算できるような、新しい極限を提案し、ゲージ、重力対応を通して、その新しい趣限の重力的な起源を解明した。
      3、Unarticle Phsicsの研究。
      共形不変な場の理論が現実に存在している場合、その物理的な帰結はUnparticle Physicsとして、加速器実験における特異な予言をする。申請者は、超対称性が現実に存在すると仮定した上で、Unparticleセクターと共存する可能性を議論した。一般に、超対称性が破れていると、その影響でUnparticleセクターの共形不変性が壊れる。この共形不変性の破れが小さくなる要請は、超対称性の破れの伝達に大きな制限を与えるととを示した。
      4、宇宙の始まりの特異性の解消の研究。
      宇宙の始まりの特異性を除去する方法を探ることは、超弦理論に課せられた一つの使命である。申請者は、次元の異なる空間の間の新しいデュアリティ(D-duality)を通して、宇宙の始まりの特異性を除去する可能性を議論した。特に、D-dualityにおけるD-braneの振る舞いを考察した。

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    • 非臨界弦理論とそれを応用した超弦理論の研究

      日本学術振興会  科学研究費助成事業 特別研究員奨励費 

      中山 優

      詳細を見る

      2005年 - 2006年

      課題番号:05J11178

      配分額:1900000円 ( 直接経費:1900000円 )

      1.2次元ブラックホール中を運動するD-braneの研究。2次元ブラックホール中を運動するD-braneを厳密に記述する境界状態を構成し、その物理的性質を調べた。特に、open-closed dualityとunitarityの両立性を厳密に示し、世界面上でのWick rotationの正しい取り扱い法を確立した。これによって、本研究者が昨年度に提唱した境界状態の構築法の正当性が明らかになった。また、量子重力的な相転移を厳密な弦理論の枠内で発見し、その具体的な性質を、境界状態を用いることで詳しく解析した。
      2.4次元超共形場理論の現象論への応用。4次元共形揚の理論を基礎にした新しい超対称性の伝達の破れの機構"conformal gauge mediation"を提唱した。このモデルは余計なパラメタを含まず、さらに超対称粒子に対して独自のスペクトラムの予言をするために、完全に実験によって、検証可能である。特に、軽いグラヴィティーノを予言するなど現象論的にも面白いモデルになっている。
      3.超対称共形場の指数の研究。超対称共形揚の理論を分類することは、場の理論・弦理論の枠組みを定めるのに重要である。超対称共系場理論の指数は超対称共形場を特徴付ける新しい量であり、その性質を詳しく調べた。具体的に、オービフォルドゲージ理論や、コニフォールドゲージ理論で指数を計算し、AdS-CFT対応から予言される結果を再現することを示した。また、有限のNに対する指数の研究を通じて、"maximally angular momentum bound"という極限を定義し、超対称指数の具体的計算を行った。さらに、重力的な観点からその極限の、重要性、物理的意味を明らかにした。

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