2025/04/02 更新

写真a

ヤマダ ユウスケ
山田 悠介
所属
附属機関・学校 高等研究所
職名
講師(任期付)

経歴

  • 2019年04月
    -
    2022年03月

    東京大学   大学院理学系研究科附属ビッグバン宇宙国際研究センター   日本学術振興会特別研究員PD

  • 2016年10月
    -
    2019年03月

    スタンフォード大学   理論物理学研究所   ポスドク研究員

  • 2016年04月
    -
    2016年09月

    慶應義塾大学   自然科学研究教育センター   ポスドク研究員

 

論文

  • More on scattering processes of dressed particles with a time-dependent mass

    Yusuke Yamada

    Physical Review D   111 ( 4 )  2025年02月  [査読有り]

     概要を見る

    We discuss the scattering process of a scalar field having a time-dependent mass with another scalar field having a constant mass as a toy model of the scattering problems during preheating after inflation. Despite a general difficulty of analytically solving such models, in our previous work [QFT approach to dressed particle processes in preheating and non-perturbative mechanism in kinematically-forbidden regime, ], we considered an exactly calculable model of such scattering processes with a time-dependent mass of the form m2(t)⊃μ4t2 and the time-dependence never disappears formally. In this work, we discuss another exactly calculable model with a time-dependent mass that has a spike/peak but asymptotes to a constant, which effectively appears in the preheating model of Higgs inflation with a nonminimal coupling. Thanks to the localized time-dependence of the mass, the daughter particle number density behaves in a physically reasonable way contrary to the one in our previous model due to the infinite time-dependent mass in the asymptotic future. On the other hand, we find that the daughter particle experiences the kinematically forbidden process, which is a nonperturbative phenomenon found in our previous work. As in the previous model, the kinematically forbidden process produces daughter particles exponentially more than the parent particle having the time-dependent mass, which never happens for particle decay processes without time-dependent backgrounds. This result supports the existence of such a nonperturbative particle production process in general time-dependent backgrounds.

    Published by the American Physical Society 2025

    DOI

  • Proving the absence of large one-loop corrections to the power spectrum of curvature perturbations in transient ultra-slow-roll inflation within the path-integral approach

    Ryodai Kawaguchi, Shinji Tsujikawa, Yusuke Yamada

    Journal of High Energy Physics   2024 ( 12 )  2024年12月  [査読有り]

     概要を見る

    We revisit one-loop corrections to the power spectrum of curvature perturbations ζ in an inflationary scenario containing a transient ultra-slow-roll (USR) period. In ref. [1], it was argued that one-loop corrections to the power spectrum of ζ can be larger than the tree-level one within the parameter region generating the seeds of primordial black holes during the USR epoch, which implies the breakdown of perturbation theory. We prove that this is not the case by using a master formula for one-loop corrections to the power spectrum obtained in ref. [2]. We derive the same formula within the path-integral formalism, which is simpler than the original derivation in [2]. To show the smallness of one-loop corrections, the consistency relations and the effective constancy of tree-level mode functions of ζ for super-Hubble modes play essential roles, with which the master formula gives a simple expression for one-loop corrections. For concreteness, we provide a reduced set of interactions including the leading-order one, while establishing the consistency relations in a self-consistent manner. We also show how the consistency relations of various operators hold explicitly, which plays a key role in proving the absence of large one-loop corrections.

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • One-Loop Vacuum Energy in 10D Super Yang–Mills Theory on Magnetized Tori with/without 4D N = 1 Supersymmetric Completion

    Hiroyuki Abe, Akinari Koichi, Yusuke Yamada

    Progress of Theoretical and Experimental Physics   2024 ( 12 )  2024年12月  [査読有り]

     概要を見る

    We compute the one-loop vacuum energy in 10-dimensional (10D) super Yang–Mills theory compactified on R1,3 × (T2)3 in the presence of the Abelian magnetic fluxes. Regularization of the infinite Kaluza–Klein (KK) sum is achieved by the use of Barnes ζ-functions, which can be applied to the case in which the KK mass spectrum has the Landau level structure. We apply the technique to two different models of the 10D super Yang–Mills theory: One is to introduce the magnetic flux background to the 10D super Yang–Mills action. The other is to first embed the 10D super Yang–Mills action into 4D N = 1 superspace and to introduce magnetic fluxes. The two models built result in different KK mass spectra as well as tree level potentials, and we compute the one-loop vacuum energy of each case. Nevertheless, both of the KK mass spectra have the Landau level structure and we can apply the regularization method in the same way. It turns out that the former model shows UV finite one-loop vacuum energy whereas the latter shows UV divergent one-loop potential that vanish when 4D N = 1 supersymmetry is not broken by magnetic fluxes. We discuss the origin of the differences from a higher-dimensional-supersymmetry viewpoint.

    DOI

    Scopus

  • Roles of electric field/time-dependent Wilson line in toroidal compactification with or without magnetic fluxes

    Hiroyuki Abe, Yusuke Yamada

    Journal of High Energy Physics   2024 ( 10 )  2024年10月  [査読有り]

     概要を見る

    We discuss the effects of electric fields along compact directions within (supersymmetric) gauge theory in ℝ1,3×T2×T2×T2. The electric field along compact directions is equivalent to time-dependent homogeneous configuration of Wilson line moduli, which would be relevant to physics in the early universe. In particular, we consider models with and without background magnetic fluxes, which lead to completely different effects of the electric field due to the difference in the Kaluza-Klein (KK) level structure. We show that, in the case without magnetic fluxes, the deceleration of KK momenta may cause non-perturbative KK particle production dubbed as the KK Schwinger effect, whereas in the case with magnetic flux such KK particle production does not take place but flavor structure of low energy effective theory may be affected.

    DOI

    Scopus

  • Roles of boundary and equation-of-motion terms in cosmological correlation functions

    Ryodai Kawaguchi, Shinji Tsujikawa, Yusuke Yamada

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   856  2024年09月  [査読有り]

     概要を見る

    We revisit the properties of total time-derivative terms as well as terms
    proportional to the free equation of motion (EOM) in a Schwinger-Keldysh
    formalism. They are relevant to the correct calculation of correlation
    functions of curvature perturbations in the context of inflationary Universe.
    We show that these two contributions to the action play different roles in the
    operator or the path-integral formalism, but they give the same correlation
    functions as each other. As a concrete example, we confirm that the Maldacena's
    consistency relations for the three-point correlation function in the slow-roll
    inflationary scenario driven by a minimally coupled canonical scalar field hold
    in both the operator and path-integral formalisms. We also give some comments
    on loop calculations.

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • Kaluza–Klein Schwinger Effect

    Yusuke Yamada

    Progress of Theoretical and Experimental Physics   2024 ( 8 )  2024年08月  [査読有り]

     概要を見る

    We show that electric fields in compactified spaces may produce Kaluza-Klein
    (KK) particles even when the energy of electric fields is smaller than KK
    scale. As an illustrating example, we consider a charged massless complex
    scalar coupled to U(1) gauge theory in $\mathbb{R}^{1,3}\times {\mathbb S}^1$
    and discuss the effect of background gauge potential along a compact direction.
    The electric field produces the charged Kaluza-Klein particle
    non-perturbatively, which we call KK Schwinger effect. We quantitatively show
    that KK modes can be produced even when the electric field energy is much below
    the KK scale. The mechanism is rather general and similar phenomena would occur
    in any compactification models when a gauge potential along compact direction
    evolves in time and experiences large enough field excursion. We also discuss
    the subtlety of four dimensional effective theory truncated by KK modes at an
    initial time, when the electric field is turned on.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Radiative correction on moduli stabilization in modular flavor symmetric models

    Tatsuo Kobayashi, Kaito Nasu, Riku Sakuma, Yusuke Yamada

    Physical Review D   108 ( 11 )  2023年12月  [査読有り]

    DOI

  • Moduli trapping mechanism in modular flavor symmetric models

    Shota Kikuchi, Tatsuo Kobayashi, Kaito Nasu, Yusuke Yamada

    Journal of High Energy Physics   2023 ( 8 )  2023年08月  [査読有り]

     概要を見る

    Abstract

    We discuss how the moduli in modular flavor symmetric models dynamically select enhanced symmetry points at which the residual modular symmetry renders extra matter fields massless. The moduli dynamics non-perturbatively produces the extra matter particles, which gives (time-dependent) effective potential that traps the moduli to enhanced symmetry points. We show analytic estimates of particle production rate consistent with numerical results, and the dynamics of moduli based on the analytic estimates.

    DOI

  • Deformation of d = 4, $$ \mathcal{N} $$ ≥ 5 supergravities breaks nonlinear local supersymmetry

    Renata Kallosh, Yusuke Yamada

    Journal of High Energy Physics   2023 ( 6 )  2023年06月  [査読有り]

     概要を見る

    Abstract

    We study d = 4, $$ \mathcal{N} $$ ≥ 5 supergravities and their deformation via candidate counterterms, with the purpose to absorb UV divergences. We generalize the earlier studies of deformation and twisted self-duality constraint to the case with unbroken local $$ \mathcal{H} $$-symmetry in presence of fermions. We find that the deformed action breaks nonlinear local supersymmetry. We show that all known cases of enhanced UV divergence cancellations are explained by nonlinear local supersymmetry.

    This result implies, in particular, that if $$ \mathcal{N} $$ = 5 supergravity at five loop will turn out to be UV divergent, the deformed theory will be BRST inconsistent. If it will be finite, it will be a consequence of nonlinear local supersymmetry and E7-type duality.

    DOI

  • QFT approach to dressed particle processes in preheating and non-perturbative mechanism in kinematically-forbidden regime

    Hidetoshi Taya, Yusuke Yamada

    Journal of High Energy Physics   2023 ( 2 )  2023年02月  [査読有り]

     概要を見る

    Abstract

    We provide a quantum-field theoretic formulation of dressed particle dynamics that systematically includes particle production and scattering/decay processes in the preheating era. Our approach is based on the so-called perturbation theory in the Furry picture, in which coherent background fields (i.e., inflaton and the expanding Universe) are treated non-perturbatively whereas interactions between dressed particles are taken into account perturbatively. As an application, we consider the instant preheating mechanism and compute the number of produced particles explicitly. We find a novel non-perturbative particle-production mechanism, which is kinematically forbidden within the conventional perturbative calculation and gives the dominant contribution in certain parameter regimes, e.g., light daughter particles.

    DOI

  • Goldstino condensation?

    Renata Kallosh, Andrei Linde, Timm Wrase, Yusuke Yamada

    Journal of High Energy Physics   2022 ( 8 )  2022年08月  [査読有り]

     概要を見る

    Abstract

    It was argued in [1] that the Volkov-Akulov (VA) model as well as similar models in supergravity and the related KKLT model in string theory, suffer from tachyonic instabilities due to goldstino condensation. The authors of [1] constructed a specific model with two unconstrained interacting chiral superfields with linearly realized supersymmetry which has an unstable vacuum. They claimed that this model becomes equivalent to the VA model in the UV limit. We show that the UV limit of their model is discontinuous, and the vacuum instability of the model proposed in [1] is not relevant to the VA model, to related models in supergravity, and to the KKLT construction.

    DOI

  • IIB String Theory and Sequestered Inflation

    Renata Kallosh, Andrei Linde, Timm Wrase, Yusuke Yamada

    Fortschritte der Physik   69 ( 11-12 )  2021年09月  [査読有り]

     概要を見る

    Abstract

    We develop sequestered inflation models, where inflation occurs along flat directions in supergravity models derived from type IIB string theory. It is compactified on a orientifold with generalized fluxes and O3/O7‐planes. At Step I, we use flux potentials which 1) satisfy tadpole cancellation conditions and 2) have supersymmetric Minkowski vacua with flat direction(s). The 7 moduli are split into heavy and massless Goldstone multiplets. At Step II we add a nilpotent multiplet and uplift the flat direction(s) of the type IIB string theory to phenomenological inflationary plateau potentials: α‐attractors with 7 discrete values . Their cosmological predictions are determined by the hyperbolic geometry inherited from string theory. The masses of the heavy fields and the volume of the extra dimensions change during inflation, but this does not affect the inflationary dynamics.

    DOI

    Scopus

    7
    被引用数
    (Scopus)
  • Sequestered Inflation

    Renata Kallosh, Andrei Linde, Timm Wrase, Yusuke Yamada

    Fortschritte der Physik   69 ( 11-12 )  2021年09月  [査読有り]

     概要を見る

    Abstract

    We construct supergravity models allowing to sequester the phenomenology of inflation from the Planckian energy scale physics. The procedure consists of two steps: At Step I we study supergravity models, which might be associated with string theory or M‐theory, and have supersymmetric Minkowski vacua with flat directions. At Step II we uplift these flat directions to inflationary plateau potentials. We find certain conditions which ensure that the superheavy fields involved in the stabilization of the Minkowski vacua at Step I are completely decoupled from the inflationary phenomenology.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Superadiabatic basis in cosmological particle production: application to preheating

    Yusuke Yamada

    Journal of Cosmology and Astroparticle Physics   2021 ( 09 ) 009 - 009  2021年09月  [査読有り]

    DOI

    Scopus

    11
    被引用数
    (Scopus)
  • Aether SUSY breaking: can aether be alternative to F-term SUSY breaking?

    Yusuke Yamada

    Journal of High Energy Physics   2021 ( 8 )  2021年08月  [査読有り]

     概要を見る

    Abstract

    We investigate supersymmetry (SUSY) breaking scenarios where both SUSY and Lorentz symmetry are broken spontaneously. For concreteness, we propose models in which scalar fluid or vector condensation breaks Lorentz symmetry and accordingly SUSY. Then, we examine whether such scenarios are viable for realistic model buildings. We find, however, that the scalar fluid model suffers from several issues. Then, we extend it to a vector condensation model, which avoids the issues in the scalar fluid case. We show that accelerated expansion and soft SUSY breaking in matter sector can be achieved. In our simple setup, the soft SUSY breaking is constrained to be less than $$ \mathcal{O}(100)\mathrm{TeV} $$ from the constraints on modification of gravity.

    DOI

  • Chiral gravitational effect in time-dependent backgrounds

    Kohei Kamada, Jun’ya Kume, Yusuke Yamada

    Journal of High Energy Physics   2021 ( 5 )  2021年05月  [査読有り]

     概要を見る

    Abstract

    Gravitational counterpart of the chiral magnetic effect, which is referred as the chiral gravitational effect, can also be of interest in a cosmological setup. In this study, we investigate this effect in the time-dependent chiral asymmetric fermion background and in the expanding spacetime by formulating the effective action of gravitational waves. We also analyze the anomaly equation to see how the backreaction from gravitational waves to thermal chiral plasma occurs. We find that the non-trivial time dependence of chiral chemical potential, which can be induced in some scenarios of baryogenesis, is the key ingredient of the chiral gravitational effect. It turns out that the “memory” of the effect is imprinted on the high frequency gravitational waves propagating in the plasma. Cosmological implications and potential effects on the gravitational wave observation are briefly discussed.

    DOI

  • Stokes phenomenon and gravitational particle production — How to evaluate it in practice

    Soichiro Hashiba, Yusuke Yamada

    Journal of Cosmology and Astroparticle Physics   2021 ( 05 ) 022 - 022  2021年05月  [査読有り]

     概要を見る

    Abstract

    We revisit gravitational particle production from the Stokes phenomenon viewpoint, which helps us make a systematic way to understand asymptotic behavior of mode functions in time-dependent background. One of our purposes of this work is to make the method more practical for evaluation of non-perturbative particle production rate. In particular, with several examples of time-dependent backgrounds, we introduce some approximation methods that make the analysis more practical. Specifically, we consider particle production in simple expanding backgrounds, preheating after R2 inflation, and a transition model with smoothly changing mass. As we find several technical issues in analyzing the Stokes phenomenon of each example, we discuss how to simplify the problems while showing the accuracy of analytic estimation under the approximations we make.

    DOI

    Scopus

    19
    被引用数
    (Scopus)
  • Particle production induced by vacuum decay in real time dynamics

    Soichiro Hashiba, Yusuke Yamada, Jun’ichi Yokoyama

    Physical Review D   103 ( 4 )  2021年02月  [査読有り]

    DOI

  • M-theory cosmology, octonions, error correcting codes

    Murat Gunaydin, Renata Kallosh, Andrei Linde, Yusuke Yamada

    Journal of High Energy Physics   2021 ( 1 )  2021年01月  [査読有り]

     概要を見る

    Abstract

    We study M-theory compactified on twisted 7-tori with G2-holonomy. The effective 4d supergravity has 7 chiral multiplets, each with a unit logarithmic Kähler potential. We propose octonion, Fano plane based superpotentials, codifying the error correcting Hamming (4, 7) code. The corresponding 7-moduli models have Minkowski vacua with one flat direction. We also propose superpotentials based on octonions/error correcting codes for Minkowski vacua models with two flat directions. We update phenomenological α-attractor models of inflation with 3α = 7, 6, 5, 4, 3, 1, based on inflation along these flat directions. These inflationary models reproduce the benchmark targets for detecting B-modes, predicting 7 different values of $$ r=12\alpha /{N}_e^2 $$ in the range 10−2 ≳ r ≳ 10−3, to be explored by future cosmological observations.

    DOI

  • Renormalization in gravitational leptogenesis with pseudo-scalar-tensor coupling

    Kohei Kamada, Jun'ya Kume, Yusuke Yamada

    Journal of Cosmology and Astroparticle Physics   2020 ( 10 ) 030 - 030  2020年10月  [査読有り]

    DOI

    Scopus

    12
    被引用数
    (Scopus)
  • Gravitational leptogenesis with kination and gravitational reheating

    Kohei Kamada, Jun'ya Kume, Yusuke Yamada, Jun'ichi Yokoyama

    Journal of Cosmology and Astroparticle Physics   2020 ( 01 ) 016 - 016  2020年01月  [査読有り]

    DOI

    Scopus

    16
    被引用数
    (Scopus)
  • Horndeski model in nonlinearly realized supergravity

    Yusuke Yamada, Jun’ichi Yokoyama

    Journal of High Energy Physics   2019 ( 12 )  2019年12月  [査読有り]

     概要を見る

    Abstract

    We construct the Horndeski Lagrangian within non-linearly realized super- gravity. We will show that the bosonic part of the Horndeski Lagrangian can be realized. Gravitino naturally couples to Horndeski sector in a super-covariant way. Such gravitino couplings are also free from ghosts.

    DOI

  • Supersymmetric anti-D3-brane action in the Kachru-Kallosh-Linde-Trivedi setup

    Niccolò Cribiori, Christoph Roupec, Timm Wrase, Yusuke Yamada

    Physical Review D   100 ( 6 )  2019年09月  [査読有り]

    DOI

  • Off-shell N = 2 → N = 1 reduction in 4D conformal supergravity

    Yusuke Yamada

    Journal of High Energy Physics   2019 ( 6 )  2019年06月  [査読有り]

     概要を見る

    Abstract

    We discussN= 2 →N= 1 reduction in four dimensional conformal supergravity. In particular, we keep the off-shell structure of supermultiplets (except hypermultiplets). As we will show, starting with (almost) off-shell conformal supergravity makes the procedure simpler than that fromN= 2 Poincaré supergravity, which makes it easier to show the correspondence to the standardN= 1 conformal supergravity. We find that theN= 1 superconformal symmetry is simply realized by truncating the gravitino multiplet. We also discuss the consistency with the originalN= 2 system and show the reducedN= 1 conformal supergravity action.

    DOI

  • Simple sinflaton-less α-attractors

    Renata Kallosh, Yusuke Yamada

    Journal of High Energy Physics   2019 ( 3 )  2019年03月  [査読有り]

     概要を見る

    Abstract

    We construct the simplest inflationary α-attractor models in supergravity: it has only one scalar, the inflaton. There is no sinflaton since the inflaton belongs to an orthogonal nilpotent superfield where the sinflaton depends on fermion bilinears. When the local supersymmetry is gauge-fixed, these models have only one single real scalar (the inflaton), a graviton and a massive gravitino. The sinflaton, sgoldstino and inflatino are all absent from the physical spectrum in the unitary gauge. The orthogonality condition leads to the simplest Kähler potential for the inflaton, while preserving the Poincaré disk geometry of α-attractors. The models are particularly simple in the framework of the $$ \overline{D3} $$ induced geometric inflation.

    DOI

  • Planck 2018 and brane inflation revisited

    Renata Kallosh, Andrei Linde, Yusuke Yamada

    Journal of High Energy Physics   2019 ( 1 )  2019年01月  [査読有り]

     概要を見る

    Abstract

    We revisit phenomenological as well as string-theoretical aspects of D-brane inflation cosmological models. Phenomenologically these models stand out on par with α-attractors, as models with Planck-compatible values of n s , moving down to the sweet spot in the data with decreasing value of r. On the formal side we present a new supersymmetric version of these models in the context of de Sitter supergravity with a nilpotent multiplet and volume modulus stabilization. The geometry of the nilpotent multiplet is evaluated in the framework of string theory.

    DOI

  • Duality Constraints on Counterterms in Supergravities

    Daniel Z. Freedman, Renata Kallosh, Yusuke Yamada

    Fortschritte der Physik   66 ( 10 )  2018年09月  [査読有り]

     概要を見る

    Abstract

    The UV finiteness found in calculations of the 4‐point amplitude in supergravity at loop order has not been explained, which motivates our study of the relevant superspace invariants and on‐shell superamplitudes for both and . The local 4‐point superinvariants for are expected to have nonlinear completions whose 6‐point amplitudes have non‐vanishing SSL's (soft scalar limits), violating the behavior required of Goldstone bosons. For , we find at that local 6‐point superinvariant and superamplitudes, which might cancel these SSL's, do not exist. This rules out the candidate 4‐point counterterm and thus gives a plausible explanation of the observed finiteness. However, at we construct a local 6‐point superinvariant with non‐vanishing SSL's, so the SSL argument does not explain the observed UV finiteness. For supergravity there are no 6‐point invariants at either or 4, so the SSL argument predicts UV finiteness.

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • On quantum compatibility of counterterm deformations and duality symmetries in $$ \mathcal{N}\ge 5 $$ supergravities

    Renata Kallosh, Hermann Nicolai, Radu Roiban, Yusuke Yamada

    Journal of High Energy Physics   2018 ( 8 )  2018年08月  [査読有り]

     概要を見る

    Abstract

    In $$ \mathcal{N}=5 $$ , 6, 8 supergravities there are hidden symmetries of equations of motion, described by duality groups SU(1, 5), SO*(12), E 7(7) respectively. UV divergences and known candidate counterterms violate the deformed duality symmetry current conservation. Extra higher derivative terms in the action are required to restore duality. We study the effect of a two-vector part of the counterterm for $$ \mathcal{N}\ge 5 $$ supergravities using the universality of the symplectic structure of extended supergravities. We construct a compact form of a deformed action with infinite number of higher derivative terms and restored duality symmetry with deformation parameter λ. We find, in λ 2 approximation, that the $$ \mathrm{S}\mathrm{U}\left(\mathcal{N}\right) $$ symmetry of the deformed theory is restored on shell.

    DOI

  • Hypernatural inflation

    Andrei Linde, Dong-Gang Wang, Yvette Welling, Yusuke Yamada, Ana Achúcarro

    Journal of Cosmology and Astroparticle Physics   2018 ( 07 ) 035 - 035  2018年07月  [査読有り]

    DOI

    Scopus

    29
    被引用数
    (Scopus)
  • Internal supersymmetry and small-field Goldstini

    Diederik Roest, Pelle Werkman, Yusuke Yamada

    Journal of High Energy Physics   2018 ( 5 )  2018年05月  [査読有り]

     概要を見る

    Abstract

    The dynamics of the Goldstino mode of spontaneously broken supersymmetry is universal, being fully determined by the non-linearly realized symmetry. We investigate the small-field limit of this theory. This model non-linearly realizes an alternative supersymmetry algebra with vanishing anti-commutators between the fermionic generators, much like an internal supersymmetry. This Goldstino theory is akin to the Galilean scalar field theory that arises as the small-field limit of Dirac-Born-Infeld theory and non-linearly realizes the Galilean symmetry. Indeed, the small-field Goldstino is the partner of a complex Galilean scalar field under conventional supersymmetry. We close with the generalization to extended internal supersymmetry and a discussion of its higher-dimensional origin.

    DOI

  • Supertrace formulae for nonlinearly realized supersymmetry

    Divyanshu Murli, Yusuke Yamada

    Journal of High Energy Physics   2018 ( 4 )  2018年04月  [査読有り]

     概要を見る

    Abstract

    We derive the general supertrace formula for a system with N chiral superfields and one nilpotent chiral superfield in global and local supersymmetry. The nilpotent multiplet is realized by taking the scalar-decoupling limit of a chiral superfield breaking supersymmetry spontaneously. As we show, however, the modified formula is not simply related to the scalar-decoupling limit of the supertrace in linearly-realized supersymmetry. We also show that the supertrace formula reduces to that of a linearly realized supersymmetric theory with a decoupled sGoldstino if the Goldstino is the fermion in the nilpotent multiplet.

    DOI

  • U(1) symmetric α-attractors

    Yusuke Yamada

    Journal of High Energy Physics   2018 ( 4 )  2018年04月  [査読有り]

     概要を見る

    Abstract

    We present a class of supergravityα-attractors with an approximate global U(1) symmetry corresponding to the axion direction. We also develop a multi-field generalization of these models and show that theα-attractor models with U(1) symmetries have a dual description in terms of a two-form superfield coupled to a three-form superfield.

    DOI

  • Fibre inflation and α-attractors

    Renata Kallosh, Andrei Linde, Diederik Roest, Alexander Westphal, Yusuke Yamada

    Journal of High Energy Physics   2018 ( 2 )  2018年02月  [査読有り]

    DOI

  • Gravitino problem in inflation driven by inflaton-polonyi Kähler coupling

    Fuminori Hasegawa, Kazunori Nakayama, Takahiro Terada, Yusuke Yamada

    Physics Letters B   777   270 - 274  2018年02月  [査読有り]

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • Ghostbusters in $f(R)$ supergravity

    Toshiaki Fujimori, Muneto Nitta, Keisuke Ohashi, Yusuke Yamada

    Journal of High Energy Physics   2018 ( 5 )  2017年12月  [査読有り]

     概要を見る

    $f(R)$ supergravity is known to contain a ghost mode associated with
    higher-derivative terms if it contains $R^n$ with $n$ greater than two.We
    remove the ghost in $f(R)$ supergravity by introducing auxiliary gauge field to
    absorb the ghost. We dub this method as the ghostbuster
    mechanism~\cite{Fujimori:2016udq}. We show that the mechanism removes the ghost
    supermultiplet but also terms including $R^n$ with $n\geq3$, after integrating
    out auxiliary degrees of freedom. For pure supergravity case, there appears an
    instability in the resultant scalar potential. We then show that the
    instability of the scalar potential can be cured by introducing matter
    couplings in such a way that the system has a stable potential.

    DOI

    Scopus

    7
    被引用数
    (Scopus)
  • Ghost-free vector superfield actions in supersymmetric higher-derivative theories

    Toshiaki Fujimori, Muneto Nitta, Keisuke Ohashi, Yusuke Yamada, Ryo Yokokura

    Journal of High Energy Physics   2017 ( 9 )  2017年08月  [査読有り]

     概要を見る

    We systematically construct ghost-free higher-derivative actions of Abelian
    vector supermultiplets in four-dimensional ${\cal N}=1$ global supersymmetric
    theories. After giving a simple example which illustrates that a naive
    introduction of a higher-derivative term gives rise to a ghost, we discuss
    possible building blocks for a ghost-free action and explicitly show that their
    bosonic parts have no ghost mode and the auxiliary field $\boldsymbol{D}$ does
    not propagate. Higher-derivative terms yield higher powers of the auxiliary
    field $\boldsymbol{D}$ in the actions, and the D-term equations of motion
    consequently admit multiple solutions in general. We confirm that the
    well-known supersymmetric Dirac-Born-Infeld action falls into this class. We
    further give another example in which the standard quadratic kinetic term
    (Maxwell term) is corrected by a quartic term of the field strength. We also
    discuss possible couplings to matter fields and a deformed D-term potential.

    DOI

    Scopus

    13
    被引用数
    (Scopus)
  • D 3 ¯ $$ \overline{D3} $$ induced geometric inflation

    Renata Kallosh, Andrei Linde, Diederik Roest, Yusuke Yamada

    Journal of High Energy Physics   2017 ( 7 )  2017年07月  [査読有り]

    DOI

  • Absence of U(1) anomalous superamplitudes in N $$ \mathcal{N} $$ ≥ 5 supergravities

    Daniel Z. Freedman, Renata Kallosh, Divyanshu Murli, Antoine Van Proeyen, Yusuke Yamada

    Journal of High Energy Physics   2017 ( 5 )  2017年05月  [査読有り]

    DOI

  • Maximal supersymmetry and B-mode targets

    Renata Kallosh, Andrei Linde, Timm Wrase, Yusuke Yamada

    Journal of High Energy Physics   2017 ( 4 )  2017年04月  [査読有り]

    DOI

  • Gravitino problem in minimal supergravity inflation

    Fuminori Hasegawa, Kyohei Mukaida, Kazunori Nakayama, Takahiro Terada, Yusuke Yamada

    Physics Letters B   767   392 - 397  2017年04月  [査読有り]

    DOI

    Scopus

    26
    被引用数
    (Scopus)
  • More on DBI action in 4D N $$ \mathcal{N} $$ = 1 supergravity

    Shuntaro Aoki, Yusuke Yamada

    Journal of High Energy Physics   2017 ( 1 )  2017年01月  [査読有り]

    DOI

  • Cosmological relaxation and high scale inflation

    Tetsutaro Higaki, Naoyuki Takeda, Yusuke Yamada

    Physical Review D   95 ( 1 )  2017年01月  [査読有り]

    DOI

  • Abelian tensor hierarchy in 4D N $$ \mathcal{N} $$ = 1 conformal supergravity

    Shuntaro Aoki, Tetsutaro Higaki, Yusuke Yamada, Ryo Yokokura

    Journal of High Energy Physics   2016 ( 9 )  2016年09月  [査読有り]

    DOI

  • Note on "Equivalence Between Different Auxiliary Field Formulations of ${\cal N}=1$ Supergravity Coupled to Matter"

    Shuntaro Aoki, Yusuke Yamada

       2016年09月

     概要を見る

    In the version 1 of this paper, we claimed that 4D ${\cal N}=1$ supergravity
    formulations with different auxiliary fields can be unified using U(1) gauge
    symmetry, whose gauge superfield does not have a kinetic term. However, after
    submission, we found a critical error in our statement. This is the note on the
    paper of the version 1.

  • Ghostbusters in higher derivative supersymmetric theories: who is afraid of propagating auxiliary fields?

    Toshiaki Fujimori, Muneto Nitta, Yusuke Yamada

    Journal of High Energy Physics   2016 ( 9 )  2016年08月  [査読有り]

     概要を見る

    We present for the first time a ghost-free higher-derivative chiral model
    with a propagating auxiliary F-term field (highest component of the chiral
    multiplet). We obtain this model by removing a ghost in a higher derivative
    chiral model, with Higgsing it in terms of an auxiliary vector superfield.
    Depending on the sign of the quadratic derivative term of the chiral
    superfield, the model contains two ghost free branches of the parameter
    regions. We find that supersymmetry is spontaneously broken in one branch while
    it is preserved in the other branch. As a consequence of dynamical F-term
    field, a conserved U(1) charge corresponding to the number density of $F$
    appears, which can be regarded as a generalization of the R-symmetry.

    DOI

    Scopus

    22
    被引用数
    (Scopus)
  • DBI action of real linear superfield in 4D N $$ \mathcal{N} $$ = 1 conformal supergravity

    Shuntaro Aoki, Yusuke Yamada

    Journal of High Energy Physics   2016 ( 6 )  2016年06月  [査読有り]

    DOI

  • de Sitter vacuum from R^2 supergravity

    Fuminori Hasegawa, Yusuke Yamada

    Physical Review D   92 ( 10 )  2015年11月  [査読有り]

    DOI

  • N = 1 $$ \mathcal{N}=1 $$ superfield description of six-dimensional supergravity

    Hiroyuki Abe, Yutaka Sakamura, Yusuke Yamada

    Journal of High Energy Physics   2015 ( 10 )  2015年10月  [査読有り]

    DOI

  • Component action of nilpotent multiplet coupled to matter in 4 dimensional N = 1 $$ \mathcal{N}=1 $$ supergravity

    Fuminori Hasegawa, Yusuke Yamada

    Journal of High Energy Physics   2015 ( 10 )  2015年10月  [査読有り]

    DOI

  • Impacts of supersymmetric higher derivative terms on inflation models in supergravity

    Shuntaro Aoki, Yusuke Yamada

    Journal of Cosmology and Astroparticle Physics   2015 ( 07 ) 020 - 020  2015年07月  [査読有り]

    DOI

    Scopus

    18
    被引用数
    (Scopus)
  • Matter coupled Dirac-Born-Infeld action in four-dimensional N=1 conformal supergravity

    Hiroyuki Abe, Yutaka Sakamura, Yusuke Yamada

    Physical Review D   92 ( 2 )  2015年07月  [査読有り]

    DOI

  • Massive vector multiplet inflation with Dirac-Born-Infeld type action

    Hiroyuki Abe, Yutaka Sakamura, Yusuke Yamada

    Physical Review D   91 ( 12 )  2015年06月  [査読有り]

    DOI

  • N =1 superfield description of vector-tensor couplings in six dimensions

    Hiroyuki Abe, Yutaka Sakamura, Yusuke Yamada

    Journal of High Energy Physics   2015 ( 4 )  2015年04月  [査読有り]

    DOI

  • Reheating processes after Starobinsky inflation in old-minimal supergravity

    Takahiro Terada, Yuki Watanabe, Yusuke Yamada, Jun’ichi Yokoyama

    Journal of High Energy Physics   2015 ( 2 )  2015年02月  [査読有り]

    DOI

  • Illustrating SUSY breaking effects on various inflation mechanisms

    Hiroyuki Abe, Shuntaro Aoki, Fuminori Hasegawa, Yusuke Yamada

    Journal of High Energy Physics   2015 ( 1 )  2015年01月  [査読有り]

    DOI

  • Inflation in supergravity without Kähler potential

    Shuntaro Aoki, Yusuke Yamada

    Physical Review D   90 ( 12 )  2014年12月  [査読有り]

    DOI

  • Natural realization of a large extra dimension in 5D supersymmetric theory

    Y. Sakamura, Y. Yamada

    Progress of Theoretical and Experimental Physics   2014 ( 9 ) 93B02  2014年09月  [査読有り]

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Erratum: Impacts of non-geometric moduli on effective theory of 5D supergravity (Journal of High Energy Physics (2013) 11 (090))

    Yutaka Sakamura, Yusuke Yamada

    Journal of High Energy Physics   2014 ( 1 )  2014年01月  [査読有り]

     概要を見る

    We correct the relation between the physical size of the extra dimension and the VEV of the moduli, and the expressions that follow from it. Errors of the sub-leading terms in section 4 are also corrected. © 2014 The Author(s).

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Impacts of non-geometric moduli on effective theory of 5D supergravity

    Yutaka Sakamura, Yusuke Yamada

    Journal of High Energy Physics   2013 ( 11 )  2013年11月  [査読有り]

    DOI

  • Instant uplifted inflation: a solution for a tension between inflation and SUSY breaking scale

    Yusuke Yamada

    Journal of High Energy Physics   2013 ( 7 )  2013年07月  [査読有り]

    DOI

  • SUSY flavor structure of generic 5D supergravity models

    Hiroyuki Abe, Hajime Otsuka, Yutaka Sakamura, Yusuke Yamada

    European Physical Journal C   72 ( 5 ) 1 - 22  2011年11月  [査読有り]

     概要を見る

    We perform a comprehensive and systematic analysis of the SUSY flavor
    structure of generic 5D supergravity models on $S^1/Z_2$ with multiple
    $Z_2$-odd vector multiplets that generate multiple moduli. The SUSY flavor
    problem can be avoided due to contact terms in the 4D effective K\"ahler
    potential peculiar to the multi-moduli case. A detailed phenomenological
    analysis is provided based on an illustrative model.

    DOI

    Scopus

    13
    被引用数
    (Scopus)

▼全件表示

講演・口頭発表等

  • モジュラーフレーバー対称性模型におけるモジュライの動的捕捉機構

    山田悠介, 菊地渉太, 小林達夫, 那須海渡, 佐久間陸, 高田翔平

    日本物理学会  

    発表年月: 2023年09月

    開催年月:
    2023年09月
     
     
  • 背景古典場中における(非)摂動的粒子散乱過程

    山田悠介, 田屋英俊

    日本物理学会  

    発表年月: 2022年09月

    開催年月:
    2022年09月
     
     
  • プレヒーティング期におけるドレスド粒子の崩壊

    山田 悠介, 田屋 英俊

    PASCOS 22  

    発表年月: 2022年07月

    開催年月:
    2022年07月
     
     
  • Nonlinearly realized supergravity and its applications

    Yusuke Yamada  [招待有り]

    APPC2019  

    発表年月: 2019年11月

  • 4次元N=1 超重力理論における反D3ブレーンの有効作用

    山田悠介, Niccolo Cribiori, Christoph Roupec, Timm Wrase

    日本物理学会2019年秋季大会  

    発表年月: 2019年09月

  • Horndeski model coupled to pure de Sitter supergravity

    Yusuke Yamada

    COSMO19  

    発表年月: 2019年09月

  • Multi-field alpha attractor in fundamental theory

    Yusuke Yamada

    YKIS2018a Symposium General Relativity-Next Generation-  

    発表年月: 2018年02月

  • Multi-field alpha attractor in fundamental theory

    Yusuke Yamada

    PASCOS 2017  

    発表年月: 2017年06月

  • 超対称/超重力理論における高階微分に伴うゴーストの除去

    山田悠介, 藤森俊明, 新田宗土, 大橋圭介

    日本物理学会 第72回年次大会  

    発表年月: 2017年03月

  • Gravitino problem in minimal supergravity inflation

    Yusuke Yamada

    New Horizon in Inflationary Cosmology  

    発表年月: 2017年03月

  • Massive vector multiplet inflation with DBI type action

    Yusuke Yamada

    COSMO-15  

    発表年月: 2015年09月

  • Inflation in supergravity without Kaehler potential

    Yusuke Yamada

    B-mode cosmology  

    発表年月: 2015年02月

  • Illustrating SUSY breaking effects on various inflation models

    Yusuke Yamada

    PASCOS 2014  

    発表年月: 2014年06月

  • LARGE volume scenario in 5D SUGRA models

    Yusuke Yamada

    PASCOS 2013  

    発表年月: 2013年11月

▼全件表示

共同研究・競争的資金等の研究課題

  • 宇宙観測による超対称性の検証

    日本学術振興会  科学研究費助成事業

    研究期間:

    2019年04月
    -
    2022年03月
     

    山田 悠介

     概要を見る

    今年度は「ストークス現象に基づく真空からの粒子生成現象の解析」、「新しい超対称性の自発的破れの機構」、「2B型超弦理論に基づくインフレーション模型の構築」を行なった。
    超対称粒子を含む重い粒子が初期宇宙において真空から生成される可能性に注目し、真空からの粒子生成現象をストークス現象の観点から系統的に解析する手法の開発を前年度から進めていた。本年度はインフレーション後に起こる爆発的な粒子生成現象であるプレヒーティングをストークス現象の観点から再考し、爆発的な粒子生成を起こす共鳴現象を含む様々なパラメータ領域での粒子生成が統一的に記述できることを示した。
    また現在の加速膨張宇宙を実現するために必要な自発的超対称性の破れの新しい機構として、ベクトル場の時間成分が真空期待値をもち、超対称性と共にローレンツ対称性も自発的に破る模型を提案した。多くの超対称模型とは異なり、超対称性の破れとローレンツ対称性の破れが相関するため、この模型における超対称性の破れのスケールは100TeVより小さくなければならないことが分かった。これはローレンツ対称性の破れの検証実験や加速器による超対称粒子の検出の双方から検証できる興味深い模型である。
    2B型超弦理論に基づくインフレーション模型の構築に関する研究も行なった。簡単な構造を持つ2B型超弦理論のコンパクト化模型には7つのモジュライ場が現れるが、単一場インフレーションの実現には6つのモジュライ場を固定する必要がある。超弦理論における無矛盾条件を考慮したフラックスパラメータを用いて、6つのもモジュライを固定した超対称性真空が実現できることを示し、残るモジュライ場をインフラトン場と同定することで、近い将来の宇宙背景放射観測により検証できるインフレーション模型を構築できることを示すことができた。

  • 物質場を含む修正超重力理論の構成とその現象論

    日本学術振興会  科学研究費助成事業

    研究期間:

    2014年04月
    -
    2016年03月
     

    山田 悠介

     概要を見る

    今年度は大きく分けて以下の3つの事柄に関しての研究を行った。一つ目は物質場及びゲージ場に対する高次微分相互作用を含む超重力模型の構成及びその宇宙論への応用である。特に超弦理論の枠組みにおける、 D-ブレーンの有効作用である、Dirac-Born-Infeld(DBI)型作用に注目した。特に、物質場とゲージ場が結合している系への拡張を初めて具体的に構成することに成功した。その系の応用として、初期宇宙におけるインフレーションモデルを構成し、DBI作用への拡張による宇宙論的影響についても調べた。その結果、DBI作用への拡張による補正によって、宇宙論的観測量が大きく変化する可能性があることを示すことができた。
    二つ目は6次元超重力理論に関する研究である。高次元時空は超弦理論の予言の一つであり、その性質を調べることは重要である。特に高次元時空の超対称性は4次元超対称性に比べて高い対称性となることも知られている。その素粒子現象論的な性質を調べるには4次元超対称性のみを明らかな形式で記述するのが有用となる。我々は6次元超重力理論を4次元超対称性が明らかな形式に書き換えることに成功した。
    三つ目はベキ零超場と呼ばれる特殊な超対称多重項を含む理論の構成である。現在の宇宙では超対称性は破れていなければならないが、その際に超対称性を破るフェルミオンが現れることが知られている。それは有効的にベキ零性を持つ超場により記述できることが知られている。本研究では特に超重力理論におけるゴールドスティーノ有効作用は完全なものを示し、さらに物質場と結合する場合について初めて具体的に示すことができた。また、その性質を持つ修正超重力理論モデルを構成した。そのモデルは宇宙観測と整合的であるだけでなく、1TeV程度の超対称性の破れを実現することを予言し、そのため近い将来の加速器実験により検証可能であること発見した。

Misc

 

現在担当している科目

 

他学部・他研究科等兼任情報

  • 理工学術院   先進理工学部

特定課題制度(学内資金)

  • 非自明な背景場中での場の量子論の研究

    2024年  

     概要を見る

    本年度は非自明な時間依存性を持つ系における場の量子論の研究に関して、大きく分けて二つのテーマを進めた。一つは時間依存する質量をもつ量子場の散乱問題である。以前の我々の研究において、時間依存する質量をもつスカラー場に関し、自由場について厳密解が存在する系を用いた摂動計算により、時間依存する質量を持つ量子場を含む粒子散乱問題では、それまでに知られていなかった新しい粒子散乱過程が存在することを初めて発見した。しかし、その模型では質量が漸近的に発散するという非物理的性質があったため、発見された散乱過程が物理的に妥当であるか疑問が残っていた。そこで私は自由場が厳密解をもつ新しい系を用いて同様の問題を考察した。今回扱った模型では粒子質量の時間依存性が漸近的に消失することから前述の非物理的な振る舞いは現れない。しかし、我々の先行研究の模型と同様に非自明な粒子散乱過程が存在することを解析計算により明らかにできた。このことから、時間依存する背景中の場の量子論特有な非自明な散乱過程は一般的な性質であることが示唆され、本研究成果は初期宇宙における宇宙の熱化過程に重要な役割を果たすことが期待される。本研究の成果は論文にまとめ、学術誌に掲載されている。二つ目は高次元時空における量子効果を含む宇宙の時間発展に関する研究である。高次元時空から有効的に4次元時空が生まれる過程の模型化を目的として、最も簡単な高次元時空宇宙模型として膨張する5次元時空宇宙模型の構成を試みた。本研究ではコンパクト化条件として比較的に簡単なものを選ぶことで量子効果等を解析計算できるようにしており、宇宙の時間発展方程式であるアインシュタイン方程式等を解析的に記述できている。最終的に量子場に伴う無限自由度を有限化した後に数値計算によるシミュレーションを実施するために、解析計算等を進めている。

  • 非自明な背景場中での場の量子論の研究

    2023年   Renata Kallosh, 小林達夫, 菊地渉太, 那須海渡, 佐久間陸, 高田翔平, 安倍博之, 小市明勢

     概要を見る

    本研究では非自明な背景場を含む場の量子論の研究というテーマのもと、以下の成果を得た。まず、「高次超対称性を持つ4次元超重力理論における紫外発散がない」ことを高次超対称性を持つ重力理論に隠れた対称性の観点から証明した。これは未だ完成していない重力の量子論における紫外発散問題に対して、超対称性とそれに伴う隠れた大局的対称性の役割の重要性を示す重要な結果である。この結果をまとめた論文は学術誌に掲載されている。また、近年注目されている「モジュラー対称性」を持つ素粒子模型において、素粒子質量の決定に重要な役割を果たす複素構造モジュライ場の真空期待値を決定する機構に関する研究も行った。複素構造モジュライ場が初期宇宙において時間変化することを想定し、その時間変化に伴って生じる真空からの粒子生成現象により生成される粒子のエネルギーを考慮することで、複素構造モジュライ場は軽い粒子が現れる「拡大対称点」周辺に捕捉される可能性に注目し、数値計算シミュレーションや解析計算を通して実際にモジュライ場が補足できることを示した。また複素構造モジュライ場に対して物質場からの量子補正により生じるポテンシャルが、拡大対称点に補足されたモジュライ場の真空期待値に与える影響を解析した。量子補正が十分に大きくなる場合、現実的な素粒子質量スペクトラムを再現するために取るべき複素構造モジュライ場の真空期待値が実現されうることを示すことに成功した。これらの結果はそれぞれ論文にまとめ、学術誌への掲載に至っている。さらに、観測されている素粒子標準理論を超弦理論の枠組みで実現する最も簡単な系として知られる「磁場を持つトーラスコンパクト化模型」における真空エネルギーに関する研究も実施した。古典的な相互作用ラグランジアンが4次元超対称性を実現するような模型において、トーラス計量に対する量子補正ポテンシャルを計算し、補正されたポテンシャルが4次元超対称性を保つ真空を持つか否かを議論した。この結果は論文にまとめ、現在学術誌で査読中である。

  • 非自明な背景古典場を含む場の量子論の研究

    2022年   Andrei Linde, Renata Kallosh, Timm Wrase, 田屋 英俊

     概要を見る

    In supergravity inflation models, a supersymmetry breaking fermion called Goldstino plays an important role to realize accelerated expansion of the Universe. It was pointed out by Dall'Agata et al. that Goldstino may form a condensation, which leads to instability to the system and successful expansion of the Universe would not occur. With Kallosh, Linde, Wrase, I showed that such condensation of Goldstino is unphysical and clarified the problem of the analysis the authors took in their paper. We have reported our result in Journal of High Energy Physics.With Taya, I have also discussed the particle scattering process in the very early Universe. In particular, just after inflation, the Universe is filled with scalar field condensate, and particles coupled to the condensate can be produced from "vacuum". We have considered the scattering processes of such particles to other light particles. We have found that due to the absence of energy conservation, parent particle produced from vacuum can decay into very light particles, which is kinematically forbidden in the standard scattering process. Interestingly, it turned out that such a kinematically forbidden process is more efficient than the kinematically allowed decay. We have reported our result at PASCOS 2022, JPS meeting and Journal of High Energy Physics.