7 events in 2022
Bethe ansatz and quantum computing
2022年1月26日22:00 - 23:15
Prof. Rafael I. Nepomechie (Professor, Physics Department, University of Miami, Florida, USA)
We begin with a brief review of the Heisenberg quantum spin chain and its remarkable solution found by Bethe. We then review a probabilistic algorithm for preparing exact eigenstates of this model on a quantum computer. An exact formula for the success probability is presented, and the computation of correlation functions is discussed. A generalization of the algorithm to open chains with boundaries is also noted.
会場: via Zoom
イベント公式言語: 英語
A simple XY model for cascade transfer
2022年1月20日13:30 - 15:00
田之上 智宏 (京都大学 大学院理学研究科)
Cascade transfer is the phenomenon that an inviscid conserved quantity, such as energy or enstrophy, is transferred conservatively from large (small) to small (large) scales. As a consequence of this cascade transfer, the distribution of the transferred quantity obeys a universal scaling law independent of the details of large (small) scales. For example, in the energy cascade in fluid turbulence, the energy spectrum follows Kolmogorov's power law [1]. Such behavior is observed even in systems different from ordinary fluids, such as quantum fluid, elastic body, and spin systems. Here, we aim to establish the concept of a universality class for cascade transfer. As a first step toward this end, we propose a simple model representing one universality class [2]. In doing so, we regard cascade transfer as a cooperative phenomenon of unidirectional transport across scales and ask how it emerges from spatially local interactions. The constructed model is a modified XY model with amplitude fluctuations, in which the spin is regarded as the “velocity” of a turbulent field in d dimensions. We show that the model exhibits an inverse energy cascade with the non-Kolmogorov energy spectrum. We also discuss the relation to spin turbulence [3,4] and atmospheric turbulence [5].
会場: via Zoom
イベント公式言語: 英語
A study of biological systems from topological point of view
2022年1月20日10:00 - 11:00
宮﨑 弘安 (数理創造プログラム 上級研究員)
A biological body can be regarded as a complicated network of chemical reactions. The chemical reaction network (CRN) is a (hyper)graph-theoretic model of such biological networks. Recently, in the joint work with Yuji Hirono, Takashi Okada and Yoshimasa Hidaka, we applied a topological method to the study of CRNs, and found a suitable way to simplify the networks. Since Professor Hirono has already explained our work in this seminar, I will try to explain it from a slightly different point of view. In the first half of the talk, I will review the entire work. In the second half, I will try to give a rough sketch of the mathematical method we used in the work.
会場: via Zoom
イベント公式言語: 英語
Axion-like particles from core-collapse supernovae
2022年1月17日11:00 - 12:00
森 寛治 (福岡大学 基盤研究機関 爆発天体研究所)
Axion-like particles (ALPs) are a class of hypothetical pseudoscalar particles which feebly interact with ordinary matter. The hot plasma of stars and core-collapse supernovae is a possible laboratory to explore physics beyond the standard model including ALPs. Once produced in a supernova, some of the ALPs can be absorbed by the supernova matter and affect energy transfer. We recently calculated the ALP emission in core-collapse supernovae and the backreaction on supernova dynamics consistently. It is found that the stalled bounce shock can be revived if the coupling between ALPs and photons is as high as g_{a gamma} ~ 10^{-9} GeV^{-1} and the ALP mass is 40-400 MeV. In this talk, I will briefly review stellar and supernova constraints on ALPs and then discuss our recent results.
会場: via Zoom
イベント公式言語: 英語
The Ohsawa-Takegoshi $L^2$ extension theorem and variations of Bergman kernels
2022年1月14日16:00 - 18:00
細野 元気 (東北大学 大学院理学研究科 数学専攻)
In complex analysis and geometry, $L^2$ methods are very important and widely used. Recent studies show that the $L^2$ theory and the variational theory are closely related. In particular, the (optimal) $L^2$ extension theorem can be proved by subharmonicity of variations of Bergman kernels and vice versa. In this talk, I will explain the background, results, and key ideas of the proof. *Please contact Keita Mikami mailing address to get access to the Zoom meeting room.
会場: via Zoom
イベント公式言語: 英語
A comprehensive view of the SARS-CoV-2 infection process
2022年1月13日10:00 - 11:00
二島 渉 (Scientist, New Mexico Consortium, Mexico)
Nishima et al. recently published a paper about a computational model of SARS-CoV-2 Spike Protein [1]. Although it is still a hypothesis due to the lack of direct experimental evidence, the story comprehensively explains the initial infection process of SARS-CoV-2 consistent with most of the empirical evidence. In the presentation, I would like to explain the overview of the infection process for the non-expert audience and how the hypothesis influences the current COVID-19 situation. If time permits, I would like to briefly explain the current plan of the iTHEMS-NMC COVID project, which is going to be the first case of undergoing an interdisciplinary collaboration framework between Japan and the US.
会場: via Zoom
イベント公式言語: 英語
Physics of nuclear bodies
2022年1月6日10:00 - 11:00
山本 哲也 (北海道大学 創成研究機構化学反応創成研究拠点 特任准教授)
Eukaryotic nucleus is not a uniform solution of DNA, but there are a number of nuclear bodies in the interchromatin spaces. There are growing number of experiments that suggest that nuclear bodies are assembled by liquid-liquid phase separation (LLPS). Condensates assembled by LLPS show coarsening or coalescence to decrease the surface energy. However, in some nuclear bodies, such as paraspeckles, nuclear stress bodies, and fibrillar centers in nucleoli, multiple condensates are stably dispersed and are not likely assembled by LLPS. The assembly mechanism of nuclear bodies is relevant to the regulation of the area of condensate surfaces, which are functional in some nuclear bodies, and the mobility of nuclear bodies. Hirose group (Osaka Univ.) has elucidated that nuclear bodies are scaffolded by a class of RNA, called architectural RNA (arcRNA), which forms complexes with RNA binding proteins. This implies that the assembly of nuclear bodies is governed RNA dynamics, such as transcription, degradation, and processing, and the sequence of bases of arcRNA. In the seminar, I will show how the base sequences and the dynamics of RNA are involved in the assembly of paraspeckles and fibrillar centers in nucleoli.
会場: via Zoom
イベント公式言語: 英語
7 events in 2022