コーヒーミーティング過去ログ
2023-09-01
New constraint on neutron star mass and radius
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)
Neutron stars are a suitable candiadte for probing the extreme states. In particular, the mass and radius constraints help us to understand the equation of state for high density matter. In this talk we show a new constraint on GRB 200415A by indentifying the observed QPOs with crustal torsional oscillations.
Public2023-08-25
Exploring Quantum Spacetime
佐藤 勇貴 (徳山工業高等専門学校 准教授)
According to Einstein’s special theory of relativity, space and time are inherently non-separable and collectively dubbed spacetime. Einstein’s another expanded theory, general relativity (GR), claims that spacetime is a dynamical entity, and the theory explains various astronomical observations very well. On the other hand, spacetime at its very beginning is supposed to be too small for GR to work properly. For such a small spacetime, quantum mechanics should play a crucial role, coming into line with GR, which may cure the situation. The spacetime that is influenced by the law of quantum mechanics is called quantum spacetime. My research is to investigate the very nature of quantum spacetime, in particular through the use of lattice discretization. In my talk, I plan to give an elementary introduction to studies of quantum spacetime.
2023-08-18
TBD
野村 泰紀 (Director, Berkeley Center for Theoretical Physics, University of California, Berkeley, USA)
2023-08-04
Current status of particle dark matter
藤原 素子 (Postdoctoral Researcher, Theoretical Particle Physics Group, Technical University of Munich, Germany)
In this talk, we will overview the current status of particle dark matter (DM). DM is a hypothetical matter that is believed to exist in our universe. We have discovered overwhelming evidence, such as rotational curves of the galaxies, but only through gravitational interaction. One interesting possibility is that DM can be an unknown elementary particle that interacts with the Standard Model (SM) particles. First, we will review particle DM candidates, search directions, and their latest results, through which we figure out the implications of theoretical properties of DM at the current stage. We also discuss new ideas to overcome limitations of the existing search directions and to probe unexplored DM parameter space comprehensively.
2023-07-28
Integral Equation Approach for Solving the Boltzmann Equation
デリック・ビーティ―・インマン (数理創造プログラム 研究員)
I will explain why integral equations can be more useful than differential equations when solving the Boltzmann equation (no knowledge of cosmology required!)
Public2023-07-14
Classical simulations of quantum computers
リナルディ エンリコ (数理創造プログラム 客員研究員 / クオンティニュアム株式会社 Quantum Machine Learning and Algorithms Senior Research Scientist)
Everything you wanted to know about quantum computers without using quantum computers. An introductory view of simulating quantum circuits and the current status of quantum computers.
2023-07-07
Long-range correlation in nonequilibrium systems
足立 景亮 (数理創造プログラム 基礎科学特別研究員 / 理化学研究所 生命機能科学研究センター (BDR) 生体非平衡物理学理研白眉研究チーム 基礎科学特別研究員)
Equilibrium states of physical systems, such as fluids and spins, typically show a short-range correlation with exponential decay, except in the symmetry-broken phase or at the critical point. In contrast, systems driven by external forces like shear flow can show a long-range correlation with power-law decay as a generic feature of nonequilibrium systems. Active matter, a crowd of self-propelled elements like bacteria or cells, is another nonequilibrium system, and its physical properties have been studied intensely. In this talk, I will overview the backgrounds and some results of our recent work that proposes a connection between externally driven systems and active matter through a long-range density correlation.
2023-06-30
Black hole image in a nutshell
チュユ・チェン (数理創造プログラム 基礎科学特別研究員)
With the recent release of the black hole images from EHT, various image features have been discovered, and some of them have even been in the spotlight among the community. Starting from the definition of photon sphere, I'll introduce some of these image features, including critical curve, photon rings, and inner shadow.
2023-06-23
Quantum Gravity and Holography
魏 子夏 (数理創造プログラム 基礎科学特別研究員)
Quantum gravity is one of the most fundamental topics in theoretical physics. In this talk, I will sketch what quantum gravity is, why physicists are curious about it, and how the concept of "holography" plays an important role in recent studies of quantum gravity.
2023-06-16
Scalable quantum simulation for correlated matters
ロンヤン・スン (数理創造プログラム 特別研究員 / 理化学研究所 計算科学研究センター (R-CCS) 量子系物質科学研究チーム 特別研究員)
In this talk, I would like to explain the scalable simulation of correlated quantum many-body systems on present noisy quantum devices. This talk is based on two recent works, arXiv:2210.14662 and arXiv:2303.17187.
2023-06-09
Tensor network methods for Quantum Computing
白川 知功 (数理創造プログラム 上級研究員 / 理化学研究所 計算科学研究センター (R-CCS) 量子系物質科学研究チーム 上級研究員)
I will briefly introduce why we are interested in tensor network methods for the use of variational quantum algorithms and quantum computing.
2023-05-26
Introduction to quotient spaces
甘中 一輝 (数理創造プログラム 基礎科学特別研究員)
The operation of taking a "quotient" often appears in mathematics. It is an operation to construct more complex objects from mathematical objects. In this coffee talk, I will give an introduction to "quotient" in geometry.
2023-05-19
Theory of diffusive shock acceleration
伊藤 裕貴 (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) 上坂スピン・アイソスピン研究室 研究員)
Particle acceleration is an ubiquitous physical process in the Universe. Diffusive shock acceleration (DSA) is widely accepted as the predominant mechanism responsible for particle acceleration in various astrophysical phenomena. This theory postulates that the energy distribution of the accelerated particles conforms to a power-law form characterized by E^{-2}. In this 15-minute talk, I will outline the derivation of this power-law index of -2 within the theory of DSA.
2023-04-28
Look up the sky at multiwavelength
辻 直美 (数理創造プログラム 客員研究員 / 神奈川大学 理学部 特別助教)
Light (i.e., photons or electromagnetic waves) provides us with important information of sources which emit the light. Measurements of light from the sky/Universe at different wavelengths can open up a different fields of physics. While my major is observations of high-energy (X-ray or gamma-ray) photons from astrophysical sources at the distance, since I moved to Kanagawa University I also work for optical measurements of nearby stars by using a telescope at the university. I will briefly introduce my current works at the coffee meeting.
2023-04-21
Discrete approximation to the Laplacian
三上 渓太 (数理創造プログラム 研究員)
In this coffee talk, I will introduce recent results on the approximation of Laplacian by discrete operators. Very modestly, the differential is a limit of difference. This modest picture is not always true if we consider differential operators. However, if one considers the norm resolvent convergence, one can show that we can approximate Laplacian by second-order difference operators. Refferences: Nakamura, S., Tadano, Y.: On a continuum limit of discrete Schrödinger operators on square lattice. J. Spectr. Theory 11 (2021), no. 1, 355-367.
Public2023-04-14
When a Cretan says all Cretans are liars
多田 司 (数理創造プログラム コーディネーター / 数理創造プログラム 副主任研究員)
The famous phrase "All Cretans are liars" said by a Cretan philosopher poses a paradox. This millenia-old paradox lies at the core of Goedel's incompleteness theorem. Recently this paradox has been discussed in the physics literature. I will introduce this recent interest and share my own thoughts.
2023-03-24
The introduce of twisted bilayer graphene
ツォン ツォン・ラ (数理創造プログラム 特別研究員)
Graphene, a two-dimensional material possessing Dirac points, is recognized as a topological semimetal. Twisted bilayer graphene, a configuration produced by rotating two layers of graphene relative to each other, can host the energy flat bands contributed by Dirac points. These flat bands serve as a fruitful playground for investigating strong correlations and topological phases, and hence the study of twisted bilayer graphene has brought excitement and impacts to the condensed matter physics community. In this coffee meeting, I will present the introduction of twisted bilayer gaphene.
2023-03-10
Theoretical analysis of supernova neutrino data
原田 了 (数理創造プログラム 基礎科学特別研究員)
A supernova explosion is the explosive death of a massive star. Neutrino observation is important to examine the mechanism. However, a theoretical framework to analyze the observed neutrinos has not been established. In order to make a tractable theory, we constructed an analytic neutrino signal model based on the Lane-Emden equation and thermal neutrino emission. Besides, to bridge the theory and observation, I developed a code, "SPECIAL BLEND," to estimate the mass and radius of the central proto-neutron star by fitting the analytic model to the supernova neutrino observation with the Bayesian approach. Using SPECIAL BLEND, I analyzed the neutrinos from the supernova SN1987A and estimated the mass and radius of the central neutron star.