理論物理学セミナー
30 イベント
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セミナー
Test of the Cosmological principle by observing the primordial gravitational waves
2022年7月27日(水)13:30 - 15:00
浦川 優子 (高エネルギー加速器研究機構 (KEK) 准教授)
In this talk, using the generalized deltaN formalism, which dramatically facilitates a computation of the primordial density perturbation and the primordial GWs (PGWs), we address a violation of the Cosmological principle, namely a violation of the global isotropy in the Universe. It’s turned out that measuring the PGWs provides a powerful tool to explore a violation of the global isotropy. If time permits, I will also discuss some prospects on LiteBIRD.
会場: コモンルーム 246-248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
Gradient flow exact renormalization group 2
2022年7月6日(水)13:30 - 17:00
鈴木 博 (九州大学 大学院理学研究院 教授)
Wilson’s exact renormalization group (ERG), which tells how a system changes under the scale transformation, provides a fundamental framework to define quantum field theory even beyond the perturbation theory. It has however been known that it is difficult to preserve a manifest gauge symmetry in ERG because of the usage of the momentum cutoff in ERG. Here, we propose a possible modification of ERG, the gradient flow exact renormalization (GFERG), which preserves a manifest gauge symmetry being based on a gauge-covariant diffusion equation. I explain the basic idea and properties of GFERG. If time permits, I want to present a possible application of GFERG to the consideration of the axial anomaly.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Gradient flow exact renormalization group 1
2022年7月5日(火)13:30 - 17:00
鈴木 博 (九州大学 大学院理学研究院 教授)
Wilson’s exact renormalization group (ERG), which tells how a system changes under the scale transformation, provides a fundamental framework to define quantum field theory even beyond the perturbation theory. It has however been known that it is difficult to preserve a manifest gauge symmetry in ERG because of the usage of the momentum cutoff in ERG. Here, we propose a possible modification of ERG, the gradient flow exact renormalization (GFERG), which preserves a manifest gauge symmetry being based on a gauge-covariant diffusion equation. I explain the basic idea and properties of GFERG. If time permits, I want to present a possible application of GFERG to the consideration of the axial anomaly.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Dress code for infrared safe S-matrix in QED
2022年6月22日(水)13:30 - 15:00
杉下 宗太郎 (名古屋大学 高等研究院 (IAR) 特任助教)
We consider the infrared (IR) aspects of the gauge invariant S-matrix in QED. I will review the problem of IR divergences in QED, and introduce the dressed state formalism to obtain IR-safe S-matrix elements. I will show a condition for dressed states to obtain IR-safe S-matrix elements, and explain that this condition can be interpreted as the memory effect and is related to asymptotic symmetry. I also explain that IR divergences are necessary to prohibit the violation of asymptotic symmetry. We also argue that the difference between dressed and undressed states can be observed, even if we are able to observe an inclusive cross-section summing over soft photons.
会場: コモンルーム 246-248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
Is the Standard Model in the Swampland? Consistency Requirements from Gravitational Scattering
2021年11月2日(火)14:30 - 16:00
青木 勝輝 (京都大学 基礎物理学研究所 基研特任助教)
Underlying assumptions on ultraviolet completion can impose constraints on its low-energy effective field theories (EFTs). The swampland program aims to clarify consistent and inconsistent EFTs with quantum gravity and aims to understand quantum gravity from low-energy physics and vice versa. One of the most well-established constraints is called positivity bounds, provided that general assumptions such as Poincare invariance and unitarity are satisfied at all scales. I will first explain how these consistency conditions arise especially in the presence of gravity. I will then show that the positivity bound is violated if the Standard Model of particle physics coupled to General Relativity is extrapolated up to 10^16 GeV, requiring new physics there or below. The precise value of the cutoff is determined by hadronic physic while it is insensitive from non-gravitational physics beyond the Standard Model. This is a signal from established physics for the necessity of quantum gravity below 10^16 GeV.
会場: コモンルーム 246-248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
S-matrix Unitarity toward UV Completion
2021年9月13日(月)13:30 - 15:00
泉 圭介 (名古屋大学 素粒子宇宙起源研究所 (KMI) 助教)
Einstein gravity is not renormalizable and does not hold perturbative unitarity at high energy. This is the main reason why the construction of quantum gravity is difficult. A conjecture was proposed by Llewellyn Smith, "renormalizablility and tree-unitarity at high energy give the same conditions for theories". This conjecture would be important because it shows that, if a theory is constructed s.t. unitarity is satisfied, renormalizablility holds automatically, and vice versa. Unfortunately, a counterexample was pointed out. If a theory involves higher derivatives, there exists a theory which is renormalizable but does not satisfy tree-unitarity. A candidate of quantum gravity, the quadratic gravity (R_{\mu\nu}^2 gravity), is one of the examples. Therefore, Llewellyn Smith's conjecture would not be useful for the discussion of quantum gravity. Then, we introduce a new conjecture, "renormalizablility and S-matrix unitarity (or often called pseudo-unitarity) at high energy give the same conditions for theories". In this talk, Llewellyn Smith's conjecture and our contribution to it will be explained. Then, our new conjecture will be introduced. Finally, it will be shown that our conjecture works well even in theories with higher derivatives.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Application of AdS/CFT to non-equilibrium phenomena in external electric fields
2021年8月16日(月)13:00 - 15:00
木下 俊一郎 (中央大学 理工学部 共同研究員)
The AdS/CFT correspondence is a useful tool for studying strongly-coupled gauge theories. According to this correspondence, the D3/D7 brane system in string theory is one of the simplest toy model dual to supersymmetric QCD-like gauge theory. In the dual field theory, the mesons, i.e., the quark-antiquark bound states are stable in vacuum when the quark is massive, while the dielectric breakdown occurs by pair production of quark-antiquark under strong electric fields. In this talk, I will review a series of our works of D3/D7 systems and show time-dependent, non-equilibrium phenomena driven by external electric fields such as suddenly increasing or rotating electric fields.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Non-Unitary TQFTs from 3d N=4 Rank-0 SCFTs
2021年7月5日(月)13:00 - 14:30
Dr. Myungbo Shim (Kyung Hee University, Republic of Korea)
We propose a novel procedure of assigning a pair of non-unitary topological quantum field theories (TQFTs), TFT_\pm[T_0], to a (2+1)D interacting N=4 superconformal field theory (SCFT) T_0 of rank 0, i.e. having no Coulomb and Higgs branches. The topological theories arise from particular degenerate limits of the SCFT. Modular data of the non-unitary TQFTs are extracted from the supersymmetric partition functions in the degenerate limits. As a non-trivial dictionary, we propose that F = max{ -log |S^{(+)}_{0\alpha}| } = max{ -log |S^{(-)}_{0\alpha}| }, where F is the round three-sphere free energy of T_0 and S^{(\pm)}_{0\alpha} is the first column in the modular S-matrix of TFT_\pm. From the dictionary, we derive the lower bound on F, F > -log(\sqrt{(5-\sqrt{5})/10}) \simeq 0.642965, which holds for any rank 0 SCFT. The bound is saturated by the minimal N=4 SCFT proposed by Gang-Yamazaki, whose associated topological theories are both the Lee-Yang TQFT. We explicitly work out the (rank 0 SCFT)/(non-unitary TQFTs) correspondence for infinitely many examples. Before going to the technical part, we provide some background materials including some peculiar features in 3d gauge theories, some supersymmetries, anyons, and some modular data of MTC in this talk.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Toward QCD-based description of dense baryonic matter
2021年6月29日(火)13:00 - 14:30
藤本 悠輝 (Postdoctoral Scholars, Department of Physics, University of Washington, USA)
The equation of state (EoS) of dense baryonic/quark matter is the crucial ingredient for understanding neutron stars. I briefly review the current state of the high-density matter EoS based on the QCD perspectives. In this talk, I particularly focus on the perturbative QCD (pQCD) EoS, which was previously thought to be useless at realistic density because it is plagued by the large uncertainty. I introduce our recent analysis of the EoS calculated within the pQCD framework with the resummation [Fujimoto & Fukushima, 2011.10891]. I discuss our scheme for the Hard Dense Loop resummation, which turns out to reduce the uncertainty compared with the conventional pQCD estimate without resummation. Our result apparently extends the applicability of the QCD-based EoS down to densities realized inside neutron stars and infers a smooth matching with the baryonic EoS.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Black Hole Information Paradox and Wormholes
2021年6月21日(月)13:00 - 14:30
後藤 郁夏人 (数理創造プログラム 基礎科学特別研究員)
In this talk, I will explain about the recent progress in the black hole information paradox that I am involved with. The information paradox arises when a black hole evaporates by emitting Hawking radiation due to the quantum effects. Time dependence of the entropy of Hawking radiation is diagnosis of information loss caused by the black hole evaporation. If information is not lost, the entropy of Hawking radiation should obey the so-called Page curve. In recent research developments, it was found that “the quantum extremal islands” reproduce the unitary Page curve in an evaporating black hole. I will argue about how the quantum extremal islands are derived from the computation of the entropy of Hawking radiation using the gravitational path-integral.
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on June 7, 2021
2021年6月7日(月)13:00 - 14:30
内藤 智也 (東京大学 大学院理学系研究科 物理学専攻 博士課程)
横田 猛 (数理創造プログラム 基礎科学特別研究員)
辻 直美 (数理創造プログラム 特別研究員)13:00-13:20 [JST] Tomoya Naito 13:20-13:40 [JST] Takeru Yokota 13:40-14:00 [JST] Naomi Tsuji 14:00- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on June 1, 2021
2021年6月1日(火)13:00 - 15:00
菊地 健吾 (数理創造プログラム 基礎科学特別研究員)
エンリコ・リナルディ (Research Fellow, Physics Department, University of Michigan, USA)
横田 宏 (数理創造プログラム 特別研究員)13:00-13:20 [JST] Kengo Kikuchi 13:20-13:40 [JST] Enrico Rinaldi 13:40-14:00 [JST] Hiroshi Yokota 14:00- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on May 31, 2021
2021年5月31日(月)13:00 - 15:00
難波 亮 (数理創造プログラム 上級研究員)
大下 翔誉 (数理創造プログラム 基礎科学特別研究員)
横倉 祐貴 (数理創造プログラム 上級研究員)
長瀧 重博 (数理創造プログラム 副プログラムディレクター)13:00-13:20 [JST] Ryo Namba 13:20-13:40 [JST] Naritaka Oshita (10 mins break) 13:50-14:10 [JST] Yuki Yokokura 14:10-14:30 [JST] Shigehiro Nagataki 14:30- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on May 25, 2021
2021年5月25日(火)13:00 - 15:00
杉浦 拓也 (数理創造プログラム 特別研究員)
土井 琢身 (理化学研究所 仁科加速器科学研究センター (RNC) 量子ハドロン物理学研究室 専任研究員)
筒井 翔一朗 (理化学研究所 仁科加速器科学研究センター (RNC) 量子ハドロン物理学研究室 基礎科学特別研究員)
後藤 郁夏人 (数理創造プログラム 基礎科学特別研究員)13:00-13:20 [JST] Takuya Sugiura 13:20-13:40 [JST] Takumi Doi (10 mins break) 13:50-14:10 [JST] Schoichiro Tsutsui 14:10-14:30 [JST] Kanato Goto 14:30- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on May 24, 2021
2021年5月24日(月)13:00 - 14:30
田屋 英俊 (数理創造プログラム 基礎科学特別研究員)
関野 裕太 (数理創造プログラム 訪問研究員)
チンカイ・チウ (数理創造プログラム 上級研究員)13:00-13:20 [JST] Hidetoshi Taya 13:20-13:40 [JST] Yuta Sekino 13:40-14:00 [JST] Ching-Kai Chiu 14:00- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on May 18, 2021
2021年5月18日(火)13:00 - 14:30
本郷 優 (Postdoctoral Research Associate, Physics Department, The University of Illinois at Chicago (UIC), USA)
伊藤 悦子 (理化学研究所 仁科加速器科学研究センター (RNC) ストレンジネス核物理研究室 協力研究員)
松本 信行 (理化学研究所 仁科加速器科学研究センター (RNC) 理研BNL研究センター 計算物理研究グループ 基礎科学特別研究員)13:00-13:20 [JST] Masaru Hongo 13:20-13:40 [JST] Etsuko Itou 13:40-14:00 [JST] Nobuyuki Matsumoto 14:00- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on May 17, 2021
2021年5月17日(月)13:00 - 14:30
初田 哲男 (数理創造プログラム プログラムディレクター)
原田 了 (数理創造プログラム 基礎科学特別研究員)
多田 司 (理化学研究所 仁科加速器科学研究センター (RNC) 量子ハドロン物理学研究室 副主任研究員)13:00-13:20 [JST] Tetsuo Hatsuda 13:20-13:40 [JST] Akira Harada 13:40-14:00 [JST] Tsukasa Tada 14:00- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
Quantum mechanical description of energy dissipation and application to heavy-ion fusion reactions
2021年2月16日(火)13:00 - 14:30
時枝 正明 (東北大学 大学院理学研究科物理学専攻 大学院生)
For theoretical description of heavy-ion fusion reactions, two different models have been used depending on the incident energy. At energies above the Coulomb barrier, importance of energy dissipation and fluctuation has been deduced from scattering experiments. To describe them phenomenologically, the classical Langevin equation has successfully been applied. At energies below the Coulomb barrier, on the other hand, the quantum coupled-channels method with a few number of internal states has been applied, and it has succeeded in explaining sub-barrier fusion reactions. While each method succeeds in each energy range, a unified description of heavy-ion fusion reactions from sub-barrier energies to above barrier energies is still missing. To achieve this, we need to treat dissipation and fluctuation quantum mechanically. In order to describe dissipation and fluctuation quantum mechanically, we have applied ideas of open quantum systems to heavy-ion fusion reactions. I will talk about recent development in this talk. First I will introduce a model Hamiltonian to treat dissipation and fluctuation quantum mechanically, and explain its character and a strategy for numerical studies. I will then apply the model to a fusion problem, and discuss a role of energy dissipation during quantum tunneling. Finally I will discuss a possible future direction for a unified description of heavy-ion fusion reactions.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Quantum kinetic theory for chiral and spin transport in relativistic heavy ion collisions and core-collapse supernovae
2021年2月4日(木)13:00 - 14:30
Dr. Di-Lun Yang (慶應義塾大学 理工学部 助教)
Recently, the anomalous transport phenomena of relativistic fermions associated with chirality and spin induced by external fields have been greatly explored in different areas of physics. Notably, such phenomena are in connection to various quantum effects such as quantum anomalies and spin-orbit interaction. The quark gluon plasmas produced from relativistic heavy ion collisions (HIC) and the core-collapse supernovae (CCSN) are both the systems in extreme conditions with high temperature or density and the presence of strong magnetic and vortical fields. Meanwhile, the abundance of light quarks and neutrinos as relativistic fermions created therein accordingly makes these two systems ideal test grounds for studying such exotic transport phenomena. Inversely, the anomalous transport may also give rise to unexpected impacts on the evolution of both systems. However, to analyze such dynamical quantum effects, a novel quantum transport theory delineating the evolution of chirality imbalance and spin has to be introduced. In this talk, I will discuss recent developments and applications of the quantum kinetic theory for chiral and spin transport in the context of HIC and CCSN.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Many body problems from quarks to stellar evolutions
2021年1月28日(木)13:30 - 15:00
安武 伸俊 (千葉工業大学 情報科学部 教育センター 准教授)
The many-body problems are major problems that need to be clarified not only in nuclear physics, but also in astronomy. In this seminar, I introduce stellar evolutions as gravitational many-body problems, and also hadronic matter as quantum many-body problems, based on the Lagrangian schemes. The macroscopic stars and the microscopic hadronic matter look completely different issues. But in this seminar, I introduce the similarities between the two problems. For hadronic matter, we adopt the color molecular dynamics to understand the behaviors and properties of hadronic matter in the framework of QCD. Although molecular dynamics can not be the first-principle, they are sometimes useful to understand many-body quantum properties. In this talk, we introduce the current status of our color molecular dynamics.
会場: via Zoom
イベント公式言語: 英語
30 イベント