Holography from field theories: a realization of AdS/CFT correspondence and beyond

2020年3月18日(水) 13:30 - 14:30

青木 愼也 (京都大学 基礎物理学研究所 教授)

*Seminar room changed from 160 to 433. We argue that the Anti-de-Sitter (AdS) geometry in $d+1$ dimensions naturally emerges from an arbitrary conformal field theory in $d$ dimensions using the free flow equation. We first show that an induced metric defined from the flowed field generally corresponds to the quantum information metric, called the Bures or Helstrom metric, if the flowed field is normalized appropriately. We next verify that the induced metric computed explicitly with the free flow equation always becomes the AdS metric when the theory is conformal. We also show that the conformal symmetry in $d$ dimensions converts to the AdS isometry in $d+1$ dimensions after $d$ dimensional quantum averaging. This guarantees the emergence of AdS geometry without explicit calculation. We next apply this method to non-relativistic systems with anisotropic scaling symmetries, such as Lifshitz field theories and Schr\”odinger invariant theories. In consequence we obtain a new hybrid geometry of Lifshitz and Schr\”odinger spacetimes as a general holographic geometry. We also show that the bulk hybrid geometry is realized by an Einstein-Maxwell-Higgs system plus a gauge fixing term for diffeomorphism, which may be interpreted as a holographic dual of a general non-relativistic system at the boundary.

会場: 研究本館 433号室

イベント公式言語: 日本語

Index of the Wilson-Dirac operator revisited: a discrete version of Dirac operator on a finite lattice

2020年2月25日(火) 16:00 - 18:10

古田 幹雄 (東京大学 教授)

The Wilson-Dirac operator is a discrete version of Dirac operator defined on regular lattices. When the discrete version is a fine approximation of the Dirac operator on a Z/2-graded Clifford module on a torus, it is known that (1) an integer-valued index is defined for the Wilson-Dirac operator, and (2) the index is equal to the Atiyah-Singer index of the Dirac operator on the torus. These have been well established up to around 2000. The strategy of all the previous works is to make use of the discrete version of the heat kernel for Neuberger's overlap Dirac operator. Therefore the strategy cannot be generalized to mod 2 index nor family version of index. In this talk I would like to explain a new approach to the index of Wilson-Dirac operator which can be immediately generalized to these various cases. Joint work with H. Fukaya, S. Matsuo, T. Onogi, S. Yamaguchi and M. Yamashita.

会場: セミナー室 (160号室)

イベント公式言語: 英語

第11回 MACSコロキウム・2019年度MACS成果報告会

2020年2月19日(水) 15:00 - 17:30

畑 浩之 (京都大学 大学院理学研究科 教授)

15:00- ティータイム 15:15- 畑 浩之 博士「弦の場の理論とその数理」 16:40- 2019年度MACS成果報告会 第11回MACSコロキウム（iTHEMS協賛）です。理研和光への配信がありますが、可能な方は是非京都で参加してください。おいしいスイーツもありますよ。

会場: 京都大学 理学部 6号館 401講義室

イベント公式言語: 日本語

Mining for Dark Matter substructure: Learning from lenses without a likelihood

2020年2月17日(月) 14:00 - 15:30

Johann Brehmer (Postdoctoral Researcher, New York University, USA)

Dr. Brehmer gives us a talk about a method to deduce DM small structures. Please join us! The subtle imprint of dark matter substructure on extended arcs in strong lensing systems contains a wealth of information about the small-scale distribution of dark matter and, consequently, about the underlying particle physics. However, teasing out this effect is challenging since the likelihood function for realistic simulations of population-level parameters is intractable. Structurally similar problems appear in many other scientific fields ranging from particle physics to neuroscience to epidemiology, which has prompted the development of powerful simulation-based inference techniques based on machine learning. We give a broad overview over these methods, and then apply them to the problem of substructure inference in galaxy-galaxy strong lenses. In this proof-of-principle application to simulated data, we show that these methods can provide an efficient and principled way to simultaneously analyze an ensemble of strong lenses, and can be used to mine the large sample of lensing images deliverable by near-future surveys for signatures of dark matter substructure.

会場: 研究本館 424-426号室

イベント公式言語: 英語

Solved and open problems regarding the neighborhood grid data structure

2020年2月7日(金) 16:00 - 18:10

スクロツキ マーティン (数理創造プログラム 客員研究員 / Fellow, German Academic Scholarship Foundation, Germany)

2020年2月7日 16:00-17:00 17:10-18:10

会場: セミナー室 (160号室)

イベント公式言語: 英語

Biology Talk

2020年2月5日(水) 16:00 - 16:30

安井 康夫 (京都大学 農学研究科 助教)

京都大学農学部の安井康夫先生に、中国雲南省での採集を含むソバの研究プロジェクトについて20-30分程度で紹介してもらいます。興味のある方はぜひお越しください。

会場: セミナー室 (160号室)

イベント公式言語: 日本語

ABBL/iTHEMS seminar - talk on ultra-high energy cosmic rays

2020年1月31日(金) 14:00 - 15:00

木戸 英治 (理化学研究所 開拓研究本部 (CPR) 長瀧天体ビッグバン研究室)

会場: セミナー室 (132号室)

イベント公式言語: 英語

Nucleon Structure from Quantum Chromodynamics

2020年1月30日(木) 11:00 - 12:00

張 家丞 (数理創造プログラム 研究員 / LBNL/UCB, USA)

Talk of this seminar is a colloquium style, so that non-expert can enjoy. Please feel free to join. The origin of matter is one of the longest standing mysteries that have captured the human imagination. The modern description of particle and nuclear physics hypothesizes that our matter filled universe must have resulted in the underlying physical processes favoring the preservation of matter over antimatter during the initial formation of our universe. This mechanism is attributed to the fundamental breaking of particle and antiparticle symmetry in physics beyond the Standard Model. One source of asymmetry is hypothesized to reside in the neutrino sector, and intense international efforts are being pursued to observe this phenomena in neutrino scattering experiments. Precise interpretation of experimental observations benefits from a Standard Model prediction of how nuclear matter interacts with neutrinos. The modern theory governing matter and their properties is the theory of the strong interaction, quantum chromodynamics (QCD). In this talk I will discuss a QCD calculation of the nucleon form factor at zero momentum transfer, which is related to how a neutrino at rest interacts with a single proton or neutron, followed by current progress on the calculation of the proton radius which is related to the slope of the form factor. Together the calculations paves a novel way forward towards a precise determination of the nucleon form factor up to momentum transfer relevant for neutrino scattering. I will end the talk by discussing future milestones and challenges as we work towards calculations for nuclear physics starting from QCD.

会場: 研究本館 433号室

イベント公式言語: 英語

量子コンピュータ研究開発の現在とこれから-量子ビットからソフトウェア・アプリケーションまで-

2020年1月29日(水) 10:00 - 18:00

会場: 鈴木梅太郎記念ホール

イベント公式言語: 日本語

CREST チュートリアル・ワークショップ

2020年1月26日(日) - 28日(火)

This workshop is co-organized by CREST Research Project "[Topology] Creation of Core Technology based on the Topological Materials Science for Innovative Devices" and RIKEN iTHEMS.

会場: 東京大学駒場キャンパス 数理科学研究科

イベント公式言語: 日本語

ABBL/iTHEMS seminar - talk on neutron stars

2020年1月24日(金) 14:00 - 15:00

祖谷 元 (数理創造プログラム 研究員 / 理化学研究所 開拓研究本部 (CPR) 長瀧天体ビッグバン研究室 研究員)

会場: セミナー室 (132号室)

イベント公式言語: 英語

Semiclassical methods in mathematical quantum mechanics

2020年1月23日(木) 16:00 - 18:10

中村 周 (学習院大学 教授)

Plan of the seminar: we separate each talk into two. In the first 60 minutes the speaker gives an introductory talk for non-mathematicians. After a short break, the second 60 minutes is spent for a bit more detailed talk for mathematicians (working in other areas). We welcome you joining both parts of the seminar or only the first/second half. Talk 1: Semiclassical analysis, microlocal analysis and scattering theory. I plan to talk about overview on the semiclassical analysis and related topics, especially its intrinsic relationship with microlocal analysis and (microlocal) scattering theory. Roughly speaking, the microlocal analysis is an application of semiclassical idea to the analysis of singularities, and its analogue in momentum space is the microlocal scattering theory. We discuss basic notions of these, and mention several recent results. Talk 2: Microlocal structure of the scattering matrix with long-range perturbations. As an example of topics discussed in Talk 1, we discuss recent results on the scattering matrix with long-range perturbations. In particular, we show that the scattering matrix is expressed as a Fourier integral operator, and in some cases we can decide its spectral properties. Our approach is fairly geometric and abstract, and thus applies not only to usual Schrödinger operators but also to higher order operators and discrete Schrödinger operators.

会場: 研究本館 435-437号室

イベント公式言語: 英語

Exploring the learning principle in the brain

2020年1月16日(木) 15:30 - 17:00

豊泉 太郎 (理化学研究所 脳神経科学研究センター (CBS) チームリーダー)

Animals adapt to the environment for survival. Synaptic plasticity is considered a major mechanism underlying this process. However, the best-known form of synaptic plasticity, i.e., Hebbian plasticity that depends on pre- and post-synaptic activity, can surge coincident activity in model neurons beyond a physiological range. Our lab has explored how neural circuits learn about the environment by synaptic plasticity. The instability of Hebbian plasticity could be mitigated by a global factor that modulates its outcome. For example, TNF-alpha that mediates homeostatic synaptic scaling is released by glia, reflecting the activity level of surrounding neurons. I show that a specific interaction of Hebbian plasticity with this global factor accounts for the time course of adaptation to the altered environment (Toyoizumi et al. 2015). At a more theoretical level, I ask what is the optimal synaptic plasticity rule for achieving an efficient representation of the environment. A solution is the error-gated Hebbian rule, whose update is proportional to the product of Hebbian change and a specific global factor. I show that this rule, suitable also in neuromorphic devices, robustly extracts hidden independent sources in the environment (Isomura and Toyoizumi 2016, 2018, 2019). Finally, I introduce that synapses change by intrinsic spine dynamics, even in the absence of synaptic plasticity. I show that physiological spine-volume distribution and stable cell assemblies are both achieved when intrinsic spine dynamics are augmented in a model (Humble et al.2019).

会場: 統合支援施設（第一食堂） 2階 大会議室

配信:計算科学研究棟 R311 / SUURI-COOL (Kyoto) / SUURI-COOL (Sendai)

イベント公式言語: 英語

Tipping point detection of nonlinear dynamics by dynamic network biomarkers, and short-term time-series data prediction by randomly distributed embedding

2020年1月15日(水) 14:00 - 16:30

Luonan Chen (Professor, Excutive director, Chinese Academy of Sciences, China)

He will talk about theoretical study on complex network data, including clinical data. His talk consists of two parts: 14:00-15:00: Detecting the tipping points of dynamic processes by dynamic network biomarkers 15:00-15:30: Coffee break 15:30-16:30: Predicting future dynamics of short-term time-series data by randomly distributed embedding First part of his talk is for general audience. In second part of his talk, he will explain mathematical basis of his study in detail.

会場: 統合支援施設（第一食堂） 2階 大会議室

イベント公式言語: 英語

Particle acceleration in young supernova remnants with X-ray and gamma-ray observations

2020年1月9日(木) 10:00 - 11:00

辻 直美

A supernova remnant (SNR) is a prominent candidate as an accelerator of galactic cosmic rays. In a widely accepted theory of diffusive shock acceleration, a particle is accelerated by diffusing back and forth across shock waves. The spectral cutoff shape of accelerated electrons is determined by diffusion and cooling and appears in the X-ray and TeV gamma-ray energy ranges, respectively, through synchrotron radiation and inverse Compton scattering. To measure the cutoff shape precisely and explore the corresponding diffusion coefficient and acceleration efficiency, we systematically analyze young SNRs that emit nonthermal X-rays and TeV gamma-rays. We found a variety of particle acceleration depending on individual SNRs: the cutoff energy is well-reproduced by the theoretical prediction in Kepler’s SNR and Tycho’s SNR, while it might be affected by the surroundings in Cassiopeia A and SN 1006. Putting all the eleven SNRs analyzed in this study together, the acceleration tends to be more efficient as the SNR evolves and becomes older, which implies a connection with turbulent production.

会場: セミナー室 (160号室)

イベント公式言語: 英語