Seminar
672 events

Seminar
Connections of Pair Correlations to Equidistribution and Additive Energy
August 31 (Thu) at 13:30  15:00, 2017
Thomas Lachmann (Graz University of Technology, Austria)
Venue: Common Room #246248
Event Official Language: English

Seminar
Pulsar Winds: Ultimate Relativistic Outflows
August 29 (Tue) at 13:30  14:30, 2017
Dmitry Khangulyan (Rikkyo University)
A highest density body that features the strongest magnetic field launches, no surprise, an ultimate outflow  pulsar wind. Despite their relativistic nature and complexity, a few simple analogies can help us to understand the essence of pulsar physics. I will present several links connecting basic mechanics and electrodynamics, everyday thermodynamics and hydrodynamics to the processes taking place in the vicinity of pulsars. These fundamental relations not only provide a simple mental image for the pulsar physics but also have their imprint in highenergy data obtained from pulsars and pulsar wind nebulae.
Venue: #433, Main Research Building
Event Official Language: English

Seminar
Joint Seminar with Condensed Matter Theory Laboratory
July 20 (Thu) at 13:30  15:00, 2017
Shinsei Ryu (Associate Professor, Department of Physics and the College, The University of Chicago, USA)
Venue: #435437, Main Research Building
Event Official Language: English

An invitation to number theory
July 10 (Mon) at 13:30  14:30, 2017
Hiroyasu Miyazaki
The goal of number theory is to reveal the mystery of natural numbers 1,2,3…. It has a long history, and it is still developing by exchanging ideas with many other branches of mathematics. In the long history, number theory had been thought of as a pure mathematics with no direct application outside mathematics. However, the rapid development of computer science changed the situation: the theory of prime numbers has been applied to code theory, cryptography, random number generation etc. It seems that there are several researches in physics and biology using the method of number theory, too. The aim of this talk is to give a beginnerfriendly introduction to number theory. Among many topics, I will focus on very fundamental and important concepts: the “padic numbers” and the “finite fields.” I hope that this talk will motivate you to relate your research to number theory.
Venue: Seminar Room #160
Event Official Language: English

Seminar
Braids and topological mixing
June 26 (Mon) at 14:00  15:00, 2017
Eiko Kin (Osaka University)
In mathematics, the braids are important tools for the knot theory, hyperbolic geometry, and dynamical systems etc. In the last ten years, the braids have been used to study mixing in fluids. Various simple mixing devices (e.g. taffy machines) have been developed. These devices utilize a particular type of braid, socalled a pseudoAnosov type. The notion of pseudoAnosov braids comes from the NielsenThurston theory on the surface automorphisms, and the theory says that the devices using pseudoAnosov braids are "efficient" in some sense. In this lecture, I will give a quick introduction of the NielsenThurston theory and the classification of braids. I will give a picture of the "complexity" forced by pseudoAnosov braids. In particular, I will explain why pseudoAnosov braids are useful and why they can be used to build interesting mixing devices. Cosponsored by RIKEN iTHEMS and AIP Mathematical Science Team
Venue: RIKEN Tokyo Liaison Office (Nihonbashi)
Event Official Language: English

Homological algebra, Renormalization and Transversality
June 26 (Mon) at 10:30  11:30, 2017
Kenji Fukaya (Permanent Member, Simons Center for Geometry and Physics, Stony Brook University, New York, USA)
Transversality is a basic concept of differential topology and theory of manifold. Homological algebra may be regarded as a method to approximate `spaces' by an algebra and is a basic concept in agebraic topology. I would like to explain in this talk how they are related to some basic problem of quantum field theory such as renormalization. Cosponsored by RIKEN iTHEMS and AIP Mathematical Science Team
Venue: RIKEN Tokyo Liaison Office (Nihonbashi)
Event Official Language: English

Galois representations and the Langlands correspondence
June 8 (Thu) at 13:30  14:30, 2017
Kazuki Tokimoto (Kyoto University)
The Langlands correspondence relates numbertheoretic objects to completely different objects. While still largely conjectural, it has attracted interests of many mathematicians over the years. It is known that the local Langlands correspondence in a special case can be constructed in a geometric way (the nonabelian LubinTate theory). In this talk, I will explain some basic concepts in mathematics (such as groups, representations and Galois groups) and then try to convey some flavor of my result related to the nonabelian LubinTate theory.
Venue: Seminar Room #160
Event Official Language: English

Atypicality of most fewbody observables
May 29 (Mon) at 13:30  14:30, 2017
Ryusuke Hamazaki (The University of Tokyo)
Understanding how isolated quantum systems thermalize has recently gathered renewed interest among theorists, thanks to the experimental realizations of such systems. The eigenstate thermalization hypothesis (ETH) is particularly investigated as a sufficient condition for the approach to thermal equilibrium. It states that diagonal matrix elements of an observable for the energy eigenstates are almost the same within a small energy shell. The ETH is justified for an observable and a Hamiltonian whose respective eigenbases are typically oriented to each other; i.e., for almost all unitary transformations of these two eigenbases with respect to the uniform Haar measure. In this seminar, we consider a Hamiltonian with fewbody interactions and random observables without assuming the uniform Haar measure. These observables are chosen in an operational manner as random linear combinations of the operator basis of spins. We show that most fewbody observables have atypical matrix elements when the energy width is not exponentially small with the system size. Namely, the maximum fluctuation for diagonal matrix elements is larger than that predicted by the uniform Haar measure.
Venue: #433, Main Research Building
Event Official Language: English

Seminar
Guiding principles to develop tough polymer materials: An exactly solvable model
May 25 (Thu) at 10:30  11:30, 2017
Naoyuki Sakumichi (Project Assistant Professor, Soft Matter Center, Ochanomizu University)
Needs to impart appropriate elasticity and high toughness to viscoelastic polymer materials are ubiquitous in industries such as concerning automobiles and medical devices. One of the major problems to overcome for toughening is catastrophic failure linked to a velocity jump [13], i.e., a sharp transition in the velocity of crack propagation occurred in a narrow range of the applied load. However, its physical origin has remained an enigma despite previous studies [4] over 35 years. Here, we propose an exactly solvable model that exhibits the velocity jump incorporating linear viscoelasticity with a cutoff length for a continuum description [5]. With the exact solution, we elucidate the physical origin of the velocity jump: it emerges from a dynamic glass transition in the vicinity of the propagating crack tip. We further quantify the velocity jump together with slow and fastvelocity regimes of crack propagation, which would stimulate the development of tough polymer materials.
Venue: Seminar Room #160
Event Official Language: English

Seminar
Chaos, Quark, Black Hole
April 14 (Fri) at 14:30  15:30, 2017
Koji Hashimoto (Professor, Department of Physics, Osaka University)
Venue: Seminar Room #160
Event Official Language: English

Seminar
HPC in precision medicine
April 11 (Tue) at 15:30  16:30, 2017
Tilo Wettig (Professor, Universität Regensburg, Germany)
In theoretical particle physics we have been using highperformance computing (HPC) for three decades to make scientific progress. Recent advances in nextgeneration sequencing, as well as the corresponding bioinformatics questions, generate an obvious need for HPC methods in the field of precision medicine. We have recently started to explore this field and believe that our HPC expertise can be used to speed up timecritical workflows, to better manage the large amount of data involved, and to lead to more cost and energyefficient solutions. I will discuss a few concrete examples, including interesting questions in singlecell sequencing.
Venue: #433, Main Research Building
Event Official Language: English

Seminar
Geometry in condensed matter physics
April 8 (Sat) at 13:00  14:00, 2017
Naoto Nagaosa (Deputy Director, Group Director, Strong Correlation Theory Research Group, RIKEN Center for Emergent Matter Science (CEMS) / Professor, Department of Applied Physics, Graduate School of Engineering, The University of Tokyo)
Quantum geometry plays essential roles current condensed matter physics. AharonovBohm effect and Berry phase as its generalization are the key concepts in electronic systems in solids, which are described by the Bloch wavefunctions and electron correlation effects on top of them. In this talk, I will describe how the geometry determines the physical properties of materials focising on the gauge structure and electomagnetic responses.
Venue: Seminar Room #160
Event Official Language: English

Seminar
The local time of simple random walks and Gaussian free fields in two dimensions
April 6 (Thu) at 10:30  11:30, 2017
Izumi Okada
By using the method of probability analysis, we have researched the local time of a multidimensionalsimple random walk. Note that the local time means the number of visits of a simple random walk to specific points in integer lattice. It is known that functionals of a local time and Gaussian free fields denote a variety of nonlinear and mathematical phenomena such as random media. Then, we are observing the relationship between two processes. As a first step, we especially observe favorite points (the singular sites where the local time is large) et al. By A.Dembo, Y.Peres, O.Zeitouni, J.Rosen, who are leading experts in this field, the importance of this point has been recently shown.
Venue: Seminar Room #160
Event Official Language: English

Fatgraph models for RNA molecules
March 23 (Thu) at 10:30  11:30, 2017
Hiroyuki Fuji (Associate Professor, Faculty of Education, Kagawa University)
Concepts of fatgraphs and partial chord diagrams occur in many branches of mathematics, including topology, geometry, and representation theory. During the last decade, some applications of these mathematical objects to the research of the molecular biology have been reported. Among them, in particular, a characterization by the genus in the fatgraph presentation of the RNA has been studied remarkably. In this talk, I will explain how the concepts of fatgraphs and partial chord diagrams are applied to the study of the secondary structure of the RNA with pseudoknots, and introduce the matrix model that is invented by basic techniques of the quantum field theory. If time permits, I shall discuss about the matrix model of the protein, and speculate about further developments.
Venue: Seminar Room #160
Event Official Language: English

TDUALITY AND SCATTERING OF STRINGY STATES
December 12 (Mon) at 15:00  16:00, 2016
Jnan Maharana
I shall first review the salient features of Tduality, paying special attentions to the worldsheet perspective. The construction of vertex operators for Moduli will be discussed. The KLT formalism will be applied to show that the Smatrix for scattering of massless state arising from toroidal compactification of closed bosonic string is Tduality invariant.
Venue: Seminar Room #160
Event Official Language: English

Nonperturabative quantum analysis based on resurgence theory
November 11 (Fri) at 10:30  11:30, 2016
Tatsuhiro Misumi (Lecturer, Akita University)
Venue: Seminar Room #160
Event Official Language: Japanese
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