理論物理学セミナー
133 イベント
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セミナー
Lecture 1 on "Modular Structures in N=4 supersymmetric Yang-Mills theory"
2025年9月18日(木) 14:30 - 17:30
Daniele Dorigoni (Associate Professor, University of Durham, UK)
In this lecture series we present recent results in the study of exact correlation functions of half-BPS operators in N=4 supersymmetric Yang-Mills theory (SYM) averaged over the space-time insertion points. After presenting some basic properties of 1/2-BPS operators in N=4 SYM, we review how these integrated correlation functions can be obtained from a matrix model formulation of the N=4 path-integral. We then move to present two different integrated correlation functions of four superconformal primary operators of the stress-tensor multiplet which are holographically related to scattering amplitudes of 4-gravitons in type IIB superstring theory on an AdS_5 x S^5 background. We derive exact expressions both in the number of colours N, as well as in the complexified Yang-Mills coupling \tau. A key player in our discussion is electro-magnetic duality of N=4 SYM which provides strong constraints on the coupling dependence of such observables which, in particular, have to be real-analytic modular invariant functions of \tau. We then discuss the large-N fixed-\tau limit to show how these results can be interpreted on the dual stringy side. We also present some details on how these integrated correlator can be used to supplement the standard bootstrap approach leading to exciting coupling dependent bounds on the anomalous dimensions of non-protected operators in N=4 SYM, such as the Konishi operator. Lastly, we discuss an integrated correlation function involving two superconformal primary operators in the stress tensor multiplet in the presence of a half-BPS line defect operator, such as a Wilson line. Electro-magnetic duality is again fundamental in understanding the exact dependence from the coupling constant \tau. [OPTIONAL: If time and energy permit, I can also present some new results regarding integrated correlation functions of two light operators, dual to gravitons on the holographic side, and heavy giant graviton operators, dual to D3 branes extended on the background geometry]
会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
Multi-strangeness matter from ab initio calculations
2025年9月16日(火) 13:30 - 15:00
童 辉 (Post-doctoral Fellow, Helmholtz-Institut für Strahlen- und Kernphysik, University of Bonn, Germany)
Hypernuclei and hypernuclear matter connect nuclear structure in the strangeness sector with the astrophysics of neutron stars, where hyperons are expected to emerge at high densities and affect key astrophysical observables. We present the first ab initio calculations that simultaneously describe single- and double- hypernuclei from the light to medium-mass range, the equation of state for -stable hypernuclear matter, and neutron star properties. Despite the formidable complexity of quantum Monte Carlo (QMC) simulations with multiple baryonic degrees of freedom, by combining nuclear lattice effective field theory with a newly developed auxiliary-field QMC algorithm we achieve the first sign-problem free ab initio QMC simulations of hypernuclear systems containing arbitrary number of neutrons, protons, and hyperons, including all relevant two- and three-body interactions. This eliminates reliance on the symmetry-energy approximation, long used to interpolate between symmetric nuclear matter and pure neutron matter. Our unified calculations reproduce hyperon separation energies, yield a neutron star maximum mass consistent with observations, predict tidal deformabilities compatible with gravitational-wave measurements, and give a trace anomaly in line with Bayesian constraints. By bridging the physics of finite hypernuclei and infinite hypernuclear matter within a single ab initio framework, this work establishes a direct microscopic link between hypernuclear structure, dense matter composition, and the astrophysical properties of neutron stars.
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
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セミナー
Exciting Possibilities of Multi-Messenger Windows on Cosmic Accelerators
2025年9月9日(火) 13:30 - 15:00
安田 航一朗 (Ph.D. Student, Department of Physics and Astronomy, University of California, Los Angeles, USA)
Active Galactic Nuclei (AGN) jets are among the most extreme particle accelerators in the universe and are thought to play a key role in the origin of ultra-high-energy cosmic rays. Yet, the physical processes inside these jets, particularly those involving heavy nuclei, remain poorly understood. In this talk, I will explore how nuclear and atomic processes in AGN jets can leave distinctive multi-messenger signatures, from neutrino production via nuclear decays to characteristic gamma-ray features from nuclear excitations. These phenomena offer a new window into the microscopic physics of nuclei under astrophysical extreme conditions, while also serving as macroscopic probes of jet composition and acceleration mechanisms. I will also discuss how upcoming observations, including neutrino flavor studies and MeV gamma-ray missions, could provide critical tests of these ideas and shed light on the role of nuclear physics in shaping cosmic accelerators.
会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
Shadow formation in gravitational collapse: redshift and blueshift by spacetime dynamics
2025年8月28日(木) 16:00 - 17:30
古賀 泰敬 (大阪工業大学 情報科学部 情報知能学科 助教)
A black hole illuminated by a background light source is observed as a black hole shadow. For a black hole formed by the gravitational collapse of a transmissive object, redshift of light due to the spacetime dynamics is expected to play a crucial role in the shadow formation. In this talk, we investigate the redshift of light caused by the spacetime dynamics. First, we consider a spherical shell model. We see that the collapse of a shell typically leads to the redshift of light, while blueshift can be also observed in some cases. This result suggests that a shadow image is generally formed in the late stage of the gravitational collapse of a transmissive object. Second, we consider a general, dynamical, spherically symmetric spacetime and propose a new covariant formula for the redshift of light. This formula relates the dynamical redshift to the energy-momentum tensor of the background spacetime and provides its intuitive interpretation with Newtonian analogy.
会場: via Zoom / セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
Analysis of inflationary models in higher-dimensional uniform inflation
2025年8月27日(水) 16:00 - 18:00
廣瀬 拓哉 (九州産業大学 教育研究施設 基礎教育サポートセンター 特任助教)
In this talk, we consider higher-dimensional uniform inflation, in which the extra dimensions expand at the same rate as three-dimensional non- compact space during inflation. We compute the cosmological perturbation in $D+4$ dimensions and derive the spectral index $n_s$ and the tensor- scalar ratio $r$. We analyze five inflationary models: chaotic inflation, natural inflation, quartic hilltop inflation, inflation with spontaneously broken SUSY, and $R^2$ inflation. By combining the results from these models with the Planck 2018 constraints, we discuss that it is not desirable for the extra-dimensional space to expand at the same rate as the three-dimensional non-compact space, except for the case of one extra dimension. This talk is based on arXiv:2501.13581[hep-ph].
会場: セミナー室 (359号室)
イベント公式言語: 英語
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セミナー
Observational constraint of non-scalar phantom dark energies
2025年8月26日(火) 16:00 - 17:30
Hsu-Wen Chiang (Postdoc, Department of Physics, Southern University of Science and Technology, China)
Recent observation of DESI strongly disfavors cosmological constant. Given the lack of constraint regarding the fundamental field that constitutes a dynamical dark energy, people traditionally resort on a hypothetical scalar field. We instead consider minimally coupled non-spinless field as alternative, specifically the extended Proca-Nuevo theory (spin-1) and 3-form field (spin-3). Both theories at the background level permit pure phantom (w < -1) and phantom crossing (w < -1 to w > -1) scenarios. Furthermore, with reasonable choice of EFT parameters we can decouple the scalar perturbation of the dark energy from the matter sector. However, the Lorentz constraint within the higher-spin field inevitably modifies the response of the scalar potential to the matter perturbation. This leads to an enhancement of the matter power spectrum most obvious in BAO fullshape analysis. We then perform MCMC analysis and show that the Hubble tension is alleviated, and the non-spin-0 models are preferred marginally over a cosmological constant.
会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
Cosmological Collider with Boundary Interactions
2025年8月7日(木) 16:00 - 17:30
Yi Wang (Professor, Department of Physics, Hong Kong University of Science and Technology, Hong Kong)
We first review cosmological collider physics. Namely, how the mass, spin, width and parity of the primordial particles during inflation may be read off from the density correlations in the CMB and the Large Scale Structure of the universe, and how this can be related to particle physics such as the Standard Model. After that, we will introduce relations between bulk and boundary terms in cosmological collider physics, and highlight a class of interactions which were overlooked in the literature.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Bridging applied math and quantum many-body physics and beyond via tensor methods
2025年7月23日(水) 16:00 - 17:00
品岡 寛 (埼玉大学)
In modern physics, high-dimensional functions and operators naturally arise in a wide range of contexts, including turbulence simulations, parameter-dependent partial differential equations (PDEs), and quantum field theory. Efficient representations and computations with such high-dimensional objects pose major challenges across disciplines. Dimensionality reduction techniques such as the Quantics Tensor Train (QTT) [1] and Tensor Cross Interpolation (TCI) [2] were originally developed in applied mathematics. In our work, we have extended these methods to quantum many-body problems, demonstrating their effectiveness in handling complex high-dimensional structures in theoretical physics [3–10]. Given their generality, QTT and TCI are expected to find applications beyond quantum theory itself, in fields such as statistical field theory, model reduction, and control of complex systems, where similar high-dimensional structures emerge. This presentation will first review the computational bottlenecks that arise in quantum many-body simulations and other high-dimensional problems. Then, we will introduce QTT and TCI from a broader, method-oriented perspective, aiming to bridge applied mathematics and quantum theoretical physics.
会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
Mesoscopic transport via one-dimensional chain with Localized two-body loss
2025年7月23日(水) 10:00 - 11:30
柿元 健佑 (早稲田大学 理工学術院 基幹理工学部 博士課程)
Mesoscopic transport has long served as a powerful probe into the quantum behavior of matter; however, the role of dissipation in such systems remains unresolved. In recent years, quantum simulations of mesoscopic systems with ultracold atomic gases have made significant progress, particularly through the use of optical tweezers to induce local dissipation via atom loss. In this talk, we discuss a two-terminal mesoscopic system in which two-body loss occurs locally at the center of a one-dimensional chain, modeling a dissipative quantum point contact. To analyze this setup, we employ the Keldysh Green’s function formalism in combination with a noise-field representation of Lindblad dynamics. Our analysis reveals that the dissipation strength depends on the occupation number of the central dissipative site, leading to a weaker suppression of particle current in the weakly dissipative regime compared to the case of one-body loss.
会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
A free probability approach to quantum chaos in random matrix ensembles
2025年7月22日(火) 16:00 - 17:00
プラティック・ナンディ (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 特別研究員)
In free probability theory, quantum chaos is marked by “free independence” between observables at early and late times, causing certain statistical measures (cumulants) to vanish. Motivated by this, we study the statistics of a time-evolved operator in the Rosenzweig-Porter (RP) random matrix ensembles. Analyzing operator statistics for different spin operators across these regimes reveals close alignment with free probability predictions in the ergodic phase, contrasted by persistent deviations in the fractal and localized phases even at late times. Using the distance measures and statistical methods, we define and characterize the onset of the free time in the ergodic phase. The talk is based on arXiv: 2506.04520.
会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
Peaks sphericity of non-Gaussian random fields
2025年7月22日(火) 10:30 - 12:00
上保 みちる (お茶の水女子大学 理学部 博士課程／日本学術振興会 特別研究員 DC)
We formulate the statistics of peaks of non-Gaussian random fields and implement it to study the sphericity of peaks. For non-Gaussianity of the local type, we present a general formalism valid regardless of how large the deviation from Gaussian statistics is. For general types of non-Gaussianity, we provide a framework that applies to any system with a given power spectrum and the corresponding bispectrum in the regime in which contributions from higher-order correlators can be neglected. We present an explicit expression for the most probable values of the sphericity parameters, including the effect of non-Gaussianity on the profile. We show that the effects of small perturbative non-Gaussianity on the sphericity parameters are negligible, as they are even smaller than the subleading Gaussian corrections. In contrast, we find that large non-Gaussianity can significantly distort the peak configurations, making them much less spherical.
会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
Starobinsky Inflation and Primordial Black Holes Production in Light of ACT, Planck and Swampland
2025年7月8日(火) 16:00 - 17:30
Sergei Ketov (東京都立大学 大学院理学研究科 物理学専攻 准教授 / 東京大学 カブリ数物連携宇宙研究機構 (Kavli IPMU) 客員研究員)
After a review of Starobinsky inflation, it is demonstrated how it fits both Planck and ACT observations, even in the presence of production of primordial black holes (as dark matter) at smaller scales. The Swampland Program constraints on the Starobinsky inflation are resolved also. Further constraints to inflation in the supergravity framework, arising via renormalization of precision LHC physics on electroweak scales are briefly outlined.
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
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セミナー
Boundary Scattering and Non-invertible Symmetries in 1+1 Dimensions
2025年7月4日(金) 14:00 - 15:00
嶋守 聡一郎 (大阪大学 大学院理学研究科 博士課程)
Recent studies by Copetti, Córdova and Komatsu have revealed that when non-invertible symmetries are spontaneously broken, the conventional crossing relation of the S-matrix is modified by the effects of the corresponding topological quantum field theory (TQFT). We extend these considerations to (1+1)-dimensional quantum field theories (QFTs) with boundaries. In the presence of a boundary, one can define not only the bulk S-matrix but also the boundary S-matrix, which is subject to a consistency condition known as the boundary crossing relation. We show that when the boundary is weakly-symmetric under the non-invertible symmetry, the conventional boundary crossing relation also receives a modification due to the TQFT effects. As a concrete example of the boundary scattering, we analyze kink scattering in the gapped theory obtained from the Φ(1,3)-deformation of a minimal model. We explicitly construct the boundary S-matrix that satisfies the Ward-Takahashi identities associated with non-invertible symmetries. This talk is based on the collaboration with Satoshi Yamaguchi.
会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
Black hole states at finite N
2025年6月18日(水) 16:30 - 17:30
Sunjin Choi (東京大学 カブリ数物連携宇宙研究機構 (Kavli IPMU) ポスドク研究員)
We study new cohomologies for the local BPS operators of the maximal super-Yang-Mills theory to better understand the black hole microstates. We first analyze the index of these black hole operators and explicitly construct their cohomologies to study how they imitate the quantum black holes. We find many towers of states and partial no-hair behaviors where certain gravtions are forbidden to dress these black hole operators. This qualitatively agrees with the behavior of the perturbative hairy BPS black holes or the so-called grey galaxies. Throughout this talk, we mainly focus on a subsector of the field theory corresponding to the BMN matrix theory, which exhibits a black hole-like entropy growth at large N.
会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
Charting the landscape of gauge-fermion dynamics
2025年6月16日(月) 13:30 - 15:00
アルバロ・パストール グティエレス (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 基礎科学特別研究員)
Gauge–fermion quantum field theories are central to our understanding of nature, from QCD to the electroweak sector. Beyond the Standard Model, strongly coupled gauge dynamics offer compelling avenues to address open puzzles. In this talk, I present a cartographic study of gauge–fermion theories across varying numbers of colours and flavours, focusing on the interplay between colour confinement and chiral symmetry breaking. We determine the flavour and colour dependence of the corresponding dynamical scales, providing a unified picture that interpolates between QCD-like regimes—where we recover quantitative agreement with lattice results—and the perturbative conformal limit. The analysis is based on the functional renormalisation group and employs a novel approximation scheme that allows for controlled and flexible access to the non-perturbative dynamics. We further explore the near-conformal regime with walking behaviour and estimate the lower boundary of the Caswell–Banks–Zaks conformal window. This framework enables a self-consistent mapping of the theory space of strongly coupled gauge–fermion systems and yields first-principles results with direct relevance for physics beyond the Standard Model.
会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
A New Holographic Entanglement Entropy in the de Sitter space
2025年6月13日(金) 16:00 - 17:00
鈴木 優樹 (京都大学 基礎物理学研究所 博士課程（学術振興会特別研究員）)
We propose a new holographic entanglement entropy in the three-dimensional de Sitter space. It is known that the holographic entanglement entropy via Ryu-Takayanagi prescription violates the entropic inequalities that they should satisfy. We propose a kind of extensions of the Ryu-Takayanagi formula so that they satisfy the strong subadditivity. We fix consistent parameter regions of the entropy and finally comment on the implications to the static patch holography.
会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
Gravitational Lensing in the Schwarzschild Spacetime: Photon Rings in Vacuum and in the Presence of a Plasma
2025年6月12日(木) 15:00 - 16:30
Torben Christian Frost (Postdoctoral Researcher, Kavli Institute for Astronomy and Astrophysics, Peking University, China)
Astrophysical black hole candidates are often surrounded by an accretion disk. In particular the interior region of this accretion disk can consist of a plasma and the trajectories of light rays travelling through this plasma can deviate significantly from the trajectories of light rays travelling through vacuum. While usually these environments are very complex we can already learn a lot about the observable features using simple plasma models. In the context of general relativity for some of these plasma models the equations of motion are fully separable and even analytically solvable. In my talk I will illustrate what we can learn from such models using the Schwarzschild spacetime as background. I will assume that the black hole is surrounded by an inhomogeneous, pressureless, and non-magnetised plasma and solve the equations of motion analytically exact. Then I will assume that we have a luminous disk in the equatorial plane and discuss the impact of the plasma on the so-called photon rings. I will discuss the changes of their geometrical structure, the redshift, and the travel time of the photons compared to photon rings in vacuum and what we can learn about the properties of the plasma. I will also discuss how the presence of the plasma may be able to help us to constrain gravity in the strong field regime. Finally, I will discuss how the obtained results will contribute to designing a multimessenger approach for probing gravity in the strong field regime in the context of the Maxwell-Einstein-Pauli Observatory.
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
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セミナー
A New Measure of Genuine Multipartite Entanglement
2025年6月6日(金) 14:00 - 15:00
Jaydeep Kumar Basak (Post-doctoral Fellow, Gwangju Institute of Science and Technology (GIST), Republic of Korea)
In this talk, I will introduce ``Latent entropy" (L-entropy) as a novel measure to characterize genuine multipartite entanglement in pure states, applicable to quantum systems with both finite and infinite degrees of freedom. This measure, derived from an upper bound on reflected entropy, attains its maximum for three-party GHZ states and $n=4,5$-party $2$-uniform states. I will also show the generalization of this measure for higher party states. Furthermore, I will discuss an analogue of the Page curve in multiboundary wormholes. If time permits, I will show the behaviour of multipartite entanglement in random states.
会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
Exotic Pairing Nature and Charge Ordering in Kagome Superconductor
2025年6月5日(木) 15:00 - 16:15
Wu Xianxin (Associate Professor, CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China)
Abstract：Recent experimental investigations have identified fascinating electronic orders in kagome metals, such as intriguing superconductivity, charge density wave (CDW) and nematicity. Notably, there is various evidence of spontaneous time-reversal symmetry (TRS) breaking within the CDW phase, pointing to a long-pursued loop current order, though its underlying mechanism remains elusive. In this talk, I will first review the exotic properties of these kagome superconductors. Then, I will discuss the effective model and the unique sublattice texture associated with van Hove singularities in the kagome lattice [1], which turns out to have significant effect on correlated states. Finally, I will present our scenario for realizing a TRS breaking CDW within the kagome lattice and discuss loop-current fluctuation induced unconventional pairing [2-4]. Potential experimental implications will be also discussed.
会場: via Zoom / 研究本館
イベント公式言語: 英語
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セミナー
Generalized symmetry from Type IIB superstring theory
2025年5月27日(火) 16:00 - 17:00
川平 将志 (神戸大学 大学院理学研究科 物理学専攻 博士研究員)
Recently, generalized symmetries have enabled the systematic analysis of various quantum systems. In this talk, we focus on global generalized symmetries that appear in the low-energy effective theory of type IIB superstring theory (i.e., type IIB supergravity). Specifically, we highlight the SL(2,ℤ) gauge symmetry (self-duality) in type IIB supergravity. We see that a global ℤ₁₂ eight-form symmetry arises as the quantum symmetry of the SL(2,ℤ) gauge symmetry. And we discuss its topological operator and its relation to 7-branes. This talk is based on joint work with Hiroki Wada (Tohoku University) and Naoto Kan (Osaka University).
会場: 研究本館 3階 359号室とZoomのハイブリッド開催 (メイン会場) / via Zoom
イベント公式言語: 英語
133 イベント