コーヒーミーティング過去ログ
2021-07-30
Conformal Bootstrap in AdS/CFT
楠亀 裕哉 (数理創造プログラム 基礎科学特別研究員 / Burke Fellow, Burke Institute, California Institute of Technology, USA)
A consistency condition for a given theory is a very vague concept, but in conformal field theories it can be formulated explicitly, known as the "conformal bootstrap equation". The main applications of the conformal bootstrap in recent years can be roughly classified into two categories: "deriving universality (of energy spectrum, etc.)" and "excluding impossible theories". Here I will introduce an application of the conformal bootstrap in the context of understanding quantum gravity.
2021-07-16
Ringing Black Holes
大下 翔誉 (数理創造プログラム 基礎科学特別研究員)
I will provide a brief review of the quasinormal modes of black holes. The study of black hole perturbations is important to model the waveform of ringdown gravitational waves emitted from binary black hole mergers or coalescences of compact objects leading to the formation of black holes. In the latter part of my talk, I will discuss the "ease of excitation" of quasinormal modes. This is indeed important to test the no-hair theorem of balck holes.
2021-07-09
Von Neumann algebras and their projections
森 迪也 (数理創造プログラム 基礎科学特別研究員)
The theory of von Neumann algebras began in a work by von Neumann in 1929. A von Neumann algebra is widely regarded as a noncommutative measure space. I am particular interested in the structure of projections of a von Neumann algebra, which play the role of measurable sets in measure theory. In this talk I will invite the audience to the mysterious world of the geometry of noncommutative measurable sets.
2021-07-02
Exact WKB and its applications to physics
田屋 英俊 (数理創造プログラム 基礎科学特別研究員)
I explain the exact WKB method, which is a method to solve ordinary differential equations and has been developed (mainly) in mathematics since 1980's. I also discuss its applications to physics, including nonperturbative particle production by strong fields, and mention open problems in this field.
2021-06-25
The wave operator and the Oppenheim conjecture
甘中 一輝 (数理創造プログラム 基礎科学特別研究員)
I am a new member of iTHEMS and working on spectral analysis of a Lorentzian manifold in mathematics.In this talk, we will discuss the eigenvalue distribution of a wave operator on flat tori as the simplest case. Through the Oppenheim conjecture about the distribution of values at integer points of indefinite quadratic forms, I would like to explain mathematically interesting aspects of spectral analysis of a wave operator. I don't know the physical meaning of this study, but I hope this talk will be an opportunity to discuss it.
2021-06-18
Phase transtion' in Kahler geometry
井上 瑛二 (数理創造プログラム 基礎科学特別研究員)
I am a new member of RIKEN iTHEMS and working on Kahler geometry in mathematics. As I cannot overview my study in this short time, I would like to explain a strange phenomenon now I am facing in Kahler geometry with a specific example. It is reminiscent of `phase transition' or `spontaneous symmetry breaking'. I hope it makes a chance of discussion with researchers in other areas.
2021-06-11
The death of a star: the theory of the supernova explosion
原田 了 (数理創造プログラム 基礎科学特別研究員)
At the end of the stellar evolution, the star explodes as bright as a galaxy and leaves a neutron star. This explosion is known as the supernova. Understanding the supernova explosion mechanism is crucial because it plays a vital role in the stellar and cosmic matter evolutions. The explosion mechanism includes a variety of physical processes, and hence it is a challenging problem. In this coffee talk, I would like to introduce the basic features of supernovae and the current understanding of the explosion mechanism.
Public2021-06-04
Canonical form of tensor networks in one and two dimensions
ヤンタオ・ウー (数理創造プログラム 特別研究員)
I will be a new member of RIKEN iTHEMS and work on computational study in condensed matter physics. In this short coffee meeting, I would like to discuss the basics of tensor networks. I will be pedagogical and not assume knowledge of quantum mechanics. I will assume basic linear algebra at the level of singular value decomposition. I will introduce the graphical notation of a tensor network, and the notion of a canonical form in one dimension. If time permits, I will also discuss the canonical form in two dimensions.
Public2021-05-28
The basics of topological band theory
ツォン ツォン・ラ (Post-doctoral research scientist, Max Planck Institute for Chemical Physics of Solids, Germany)
I will be a new member of RIKEN iTHEMS and work on theoretical study in condensed matter. In this short coffee meeting, I would like to disuss the topology properties of photocurrent. Firstly, based on band theory, I will discuss the topological classification of crystalline materials. Secondly, Similar to direct current formular I=U/R, the photocurrents will be discussed. Finally, I will discuss the topology properties of photocurrent in the various topological semimetals.
2021-05-21
Cosmology 101 - expanding universe and inflationary cosmology
難波 亮 (数理創造プログラム 上級研究員)
I am a new member of RIKEN iTHEMS and working on several aspects of theoretical cosmology. As a partial self-introduction and introduction to the field, I would like to discuss some basics of cosmology, making it accessible by the iTHEMS members in different areas of expertise. In this short coffee meeting talk, my main focus is the evolution of the universe and the physics during its earliest period.
2021-05-14
Reducing complexity and pursuing reality in computational biophysics
杉田 有治 (数理創造プログラム 上級研究員 / 理化学研究所 開拓研究本部 (CPR) 杉田理論分子科学研究室 主任研究員)
The basic unit of all the living matters is a cell, where huge number of biomolecules exist and express their biological functions. When we aim to study biological systems in computational biophysics, we always encounter many problems originated from the complexity of the systems. Reducing complexity has been one of the most essential issues in computational biophysics, while too much simplifications may lose the reality of biological phenomena. I would like to discuss several key mathematical concepts that have been used in computational biophysics for reducing complexity and pursuing reality of biology in the cell.
2021-04-30
Computational phases of quantum matter
松浦 俊司 (数理創造プログラム 客員研究員 / Fundamental Researcher, Quantum Simulation Division, 1QBit, Canada)
I will talked about a connection between measurement-based quantum computing and quantum phases in physics.
Public2021-04-23
Building something from nothing: a mathematical framework for aperiodic/amorphous sets
クリストファー・ボーン (数理創造プログラム 客員研究員 / 東北大学 材料科学高等研究所 (AIMR) 助教)
I will introduce a mathematical construction due to Bellissard that allows us to study disordered materials via Delone sets.
2021-04-16
Density Functional Theory from Functional Renormalization Group
横田 猛 (数理創造プログラム 基礎科学特別研究員 / 東京大学 物性研究所 特別研究員)
In this talk, I will give a brief introduction of density functional theory. I will also talk about our recent attempt to improve density functional theory for electron systems by use of the functional renormalization group.
2021-04-02
Spin transport in ultracold atomic superfluids
関野 裕太 (数理創造プログラム 訪問研究員)
I will briefly introduce transport phenomena of spin in ultracold atomic gases in a superfluid phase
2021-03-26
Hunting the standard candles in their own nest
マリア・ジョヴァンナ・ダイノッティ (NAOJ/Space Science Institute)
I will introduce briefly the concept of Standard candles and how Gamma-Ray Bursts can be used as standardized candles through a new three-dimensional relation among important features of GRBs and how the kilonovae events associated with GRBs form a plane can naturally form a different plane with a much smaller dispersion around the plane.
2021-03-19
Sensitivity and robustness of chemical reaction network systems
岡田 崇 (数理創造プログラム 上級研究員)
In living cellls, many reactions occur and form complex networks, such as metabolic networks. I will discuss how biological functions can emerge from the complex network dynamics, from network topology perspectives.
2021-02-26
Fermionic transport under gravity
Kazuya Mameda (QHP)
I will briefly talk about transport phenomena induced by a background gravitational field.
2021-02-19
information scrambling is growth of wormwhole
野﨑 雅弘 (数理創造プログラム 基礎科学特別研究員)
I will explain what is the information scrambling, why it is important, and how it is related to the growth of wormhole.