Seminar
628 events

Semiclassical defect measures and observability estimate for Schrödinger operators with homogeneous potentials of order zero
October 30 (Wed) at 8:40  10:00, 2019
Keita Mikami (Research Scientist, iTHEMS)
Seminar will be held from 15:40 to 17:00 on Oct.29(PDT, the U.S. Pacific Daylight Time) as a Harmonic Analysis and Differential Equations Seminar.
Venue: UC Berkeley
Event Official Language: English

Seminar
AtiyahHirzebruch spectral sequence in the band theory
October 24 (Thu) at 16:00  18:10, 2019
Ken Shiozaki (Assistant Professor, Yukawa Institute for Theoretical Physics, Kyoto University)
Plan of the seminar: we separate each talk into two. In the first 60 minutes the speaker gives an introductory talk for nonmathematicians. 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. Abstract: The topological nature of the band theory in crystalline systems can be well described by the topological Ktheory over the Brillouin zone torus. In the first part of my talk, I will present the bandtheory understanding of the grading of the Kgroup, and how the exactness axiom and the MayerVietoris sequence are naturally understood. In the second part, I discuss how to compute the differentials of the AtiyahHirzebruch spectral sequence associated with a cell decomposition.
Venue: Seminar Room #160
Event Official Language: English

Seminar
Mean dimension of dynamical systems and information theory
October 21 (Mon)  23 (Wed), 2019
Masaki Tsukamoto (Professor, Kyushu University)
Oct.21 15:3016:30, 16:4017:40, Okochi Hall Oct.22 13:3014:30, room #435437, Main Research Building Oct.23 13:3014:30, room #435437, Main Research Building
Venue: Okochi Hall / #435437, Main Research Building
Event Official Language: Japanese

Seminar
Haloes at the lowmass end in wino dark matter
October 21 (Mon) at 13:00  15:00, 2019
Toyokazu Sekiguchi (Research Center for the Early Universe (RESCEU), The University of Tokyo)
Neutral wino is a natural candidate of dark matter in splitsupersymmetry. Indirect detection is a promising probe of wino dark matter, with its annihilation enhanced nonperturvatively (i.e. Sommerfeld enhancement). In theoretical prediction, halo formation at the lowmass end is a key ingredient. For this purpose, we investigate kinetic decoupling of wino dark matter and consequent dark matter density perturbations. We show that inelastic processes involving charged wino, which are relevant for kinetic equilibrium at late times, shuts off abruptly. This results in boosted acoustic peaks in density power spectrum at horizon scales around the kinetic decoupling. Based on an analytic modeling of subhalo evolution, we estimate the subhalo mass function of (dwarf) galaxysized haloes and effects on the annihilation boost factor. We also discuss application of our analysis to SU(2)_L multiplet minimal dark matter.
Venue: Seminar Room #160
Event Official Language: English

Introduction to 1QBit Open Software QEMIST "QuantumEnabled Molecular ab Initio Simulation Toolkit"
October 17 (Thu) at 13:30  15:00, 2019
Shunji Matsuura (Fundamental Researcher, Quantum Simulation Division, 1QBit, Canada)
Venue: #433, Main Research Building
Event Official Language: English

Dark matter search in extended dwarf spheroidal galaxies with CTA
October 11 (Fri) at 14:00  15:00, 2019
Nagisa Hiroshima (Postdoctoral Researcher, iTHEMS)
The nature of dark matter (DM) is still a big mystery. Among the varieties of candidates, Weakly Interacting Massive Particle (WIMP) is one of the most promising ones. Gammaray observations of dwarf spheroidal galaxies (dSphs) by Fermi satellites put the strongest constraints at mDM<~ a few hundreds of GeV. In the near future, Cherenkov Telescope Array (CTA) starts its operations and expect to probe WIMP of mDM>~O(1)TeV. Different from previous experiments, spatial distributions of DM in dSphs are resolved with CTA. In this talk, I explain how it affects our accessibility to DM annihilation crosssection.
Venue: Seminar Room #132
Event Official Language: English

Seminar
Finite N corrections to the superconformal index from D3brane analysis in AdS_5/CFT_4
October 8 (Tue) at 15:30  17:00, 2019
Reona Arai (Ph.D. Student, Tokyo Institute of Technology)
In the context of the AdS/CFT, the Type IIB superstring theory on AdS_5 \times SE_5 corresponds to an N=1 quiver gauge theory, where SE_5 is a fivedimensional SasakiEinstein manifold. We study this correspondence by using the superconformal index, which contains the information of the BPS spectrum in the theory. It is known that the index of the large N limit is evaluated by the KaluzaKlein modes on SE_5 and the agreement with CFT results was confirmed in many examples. In this talk, we consider the finite N corrections to the index on the gravity side as a next step. To do this, we focus on a single D3brane wrapped around a threecycle on SE_5. Because there are in general several threecycles on SE_5, we need to sum up contributions of these single D3branes. By using the D3brane analysis, we propose a prescription to calculate the finite N corrections to the index. We explain our prescription through some examples and see the agreement with the CFT results calculated by the localization method.
Venue: Seminar Room #160
Event Official Language: English

A new lamppost in dark matter searches: Composite Dark Matter
October 1 (Tue) at 10:00  18:00, 2019
Enrico Rinaldi (Research Parttime Worker Ⅰ, iTHEMS)
In the search for the nature of dark matter many particle physics models are proposed. Models originating from a new strongly coupled dark sector, similar to QCD and Nuclear Physics, give rise to Composite Dark Matter particles. These models are hard to study, but they have a very interesting phenomenology with clear signals that are distinct from the usual WIMP candidates. To make robust predictions in Composite Dark Matter models one often needs to investigate nonperturbative effects due to the strong dynamics. In my talk I will explain how Lattice Field Theory methods and numerical simulations are well suited for this task and contribute to a solid uncertainty quantification. A variety of detection signals can be studied with lattice simulations, from dark matter self interactions to interactions with regular matter and even signals of dark phase transitions generating primordial gravitational waves.
Venue: #424426, Main Research Building
Event Official Language: English

Seminar
Angular power spectrum analysis on current and future highenergy neutrino data
September 18 (Wed) at 14:00  15:00, 2019
Ariane Dekker (Faculty of Science, University of Amsterdam, Netherlands)
The astrophysical neutrino events that have been measured in the last couple of years show an isotropic distribution on the sky. To constrain the contribution of source populations to the observed neutrino sky, we consider isotropic and anisotropic components of the diffuse neutrino data. We simulate throughgoing muon neutrino events by applying statistical distributions for the fluxes of extragalactic sources and investigate the sensitivities of current (IceCube) and future (IceCubeGen2 and KM3NeT) experiments. I will show that the angular power spectrum is a powerful probe to assess the angular characteristics of neutrino data and demonstrate that we are already constraining rare and bright sources with current IceCube data. In addition, I will investigate the decay and annihilation of very heavy dark matter as a potential neutrino source suggested by the excess in HESE data. We apply our angular power spectrum analysis to HESE data for different channels, allowing us to interpret the observed neutrino sky and perform a sensitivity forecast.
Venue: #160, 1F, Main Research Building
Event Official Language: English

Seminar
iTHEMS Biology Seminar
September 13 (Fri) at 15:00  17:20, 2019
Hiroyuki Kubota (Professor, Medical Institute of Bioregulation, Kyushu University)
Yasufumi Uezu (Researcher, Sensory And Motor Research Group, NTT Communication Science Laboratories)Timetable 15:0016:00 Hiroyuki Kubota (Kyushu Univ.) 16:0016:20 Break 16:2017:20 Yasufumi Uezu (NTT) Time: 15:0016:00 Speaker: Hiroyuki Kubota (Kyushu Univ.) Title: Regulation of insulin action by temporal patterns of insulin Abstract: Cells respond to various extracellular stimuli through a limited number of signaling pathways. One strategy to process such stimuli is to code the information into the temporal patterns of molecules. Almost all hormones exhibit distinct temporal patterns and the importance of their patterns has been reported. However, the mechanisms of how hormones regulate downstream molecules depending on their temporal patterns remain unknown. We focused on insulin which plays crucial roles on glucose homeostasis and shows several temporal patterns in vivo. In this study, we show how the Insulin signaling pathway processes the information encoded into the temporal patterns of blood insulin using a cultured cell line and mice. We found that insulin patterns selectively regulate the insulinAKT pathway, metabolites, and mRNAs. Mathematical modeling revealed the mechanisms via differences in network structures and from sensitivity and time constants. Given that almost all hormones exhibit distinct temporal patterns, temporal coding may be a general principle of system homeostasis by hormones. Time: 16:2017:20 Speaker: Yasufumi Uezu (NTT) Title: Sourcefilter interaction brings various representation in speech and singing voice Abstract: Speech plays a very important role in human communication. The sourcefilter interaction, a model that takes into account the actual speech production process, assumes that the sound source generation mechanism and the vocaltract filter are not independent, but affect each other physiologically and acoustically. It is known that the sourcefilter interaction brings about nonlinearity of speech and singing, such as singing voice with a loud volume and wide pitch range like an opera singer, or voice register transition where the vocal suppression and/or the voice pitch jump occurs. I would like to introduce my researches targeting nonlinear vocalization phenomena due to the sourcefilter interaction and results of measuring and analyzing the time waveform of speech sound and vocalfold vibrations through measurement experiments.
Venue: #424426, Main Research Building
Event Official Language: Japanese

Seminar
Introduction to quantum manybody system
September 5 (Thu)  6 (Fri), 2019
Hosho Katsura (Associate Professor, Department of Physics, Graduate School of Science, The University of Tokyo)
Venue: #535537, Main Research Building / #435437, Main Research Building
Event Official Language: Japanese

Introduction to Quantum Annealing: from Fundamentals to Applications
September 2 (Mon)  3 (Tue), 2019
Hirotaka Irie (Visiting Scientist, iTHEMS / Assistant Manager, DENSO Corporation)
Sep. 2 (Mon) 10:3012:00, 13:3015:00, 15:3017:00 Lecture 1: What is quantum annealing and quantum computation? Lecture 2: Quatum Ising models as fluxqubit degree of freedom Lecture 3: Basic usage of quantum annealer Sep. 3 (Tue) 10:3012:00, 13:3015:00, 15:3017:00 Lecture 4: Optimization problems and computational complexity Lecture 5: Realworld applications Lecture 6: Some other topics Room: 435437 (main research building): Sep.2 (Mon) am 424426 (main research building): Sep.2 (Mon) pm & Sep.3 (Tue) am+pm Abstract: Quantum annealing is a quantumcomputational scheme which tackles computationally hard optimization problems. Its quantummechanically implemented machine, called quantum annealer, is commercially manufactured by DWave Systems, Inc., and is currently available with more than 2000 quantum bits. In this twoday lecture, I would like to discuss fundamental aspects of quantum annealing (1st day) and its realworld applications (2nd day). In particular, I try to overview the current status of the machine and several problems which we should theoretically overcome. In the first day, I will start with discussing what is quantum annealing and then review how quantum Ising model is implemented with fluxqubit degree of freedom. Later on, I will discuss the basic usage of the quantum annealer as a preparation for applications. In the second day, I will first summarize several classes of optimization problems and their computational complexity, and then discuss examples of realworld applications of quantum annealing. Finally, if I have enough time, I would like to discuss other related topic on quantum annealing.
Venue: #435437, Main Research Building / #424426, Main Research Building
Event Official Language: English

Physics of GammaRay Bursts: Emission Mechanism, Particle Acceleration, Nucleosynthesis, and Gravitational Waves
August 17 (Sat) at 12:00  13:00, 2019
Shigehiro Nagataki (Deputy Program Director, iTHEMS / Chief Scientist, Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))
GammaRay Bursts (GRBs) are very powerful, special explosions of massive stars. In the explosions, highly relativistic jets are launched from progenitor stars and lots of gammarays are emitted from the jets. It is also suggested by gravitational wave detection with followup observations that (short duration) GRBs are triggered by neutron star mergers (NSMs). In this talk, physics of GRBs are introduced with some of our recent studies. I would like to introduce how the relativistic jets will emit bunch of gammarays, and how particle acceleration happens in the relativistic jets. I also would like to introduce our recent studies on rprocess nucleosynthesis & gravitational wave emission at NSMs. Location: 50A5132
Venue: Lawrence Berkeley National Laboratory (Berkeley, California)
Event Official Language: English

Seminar
Complex analysis on a neighborhood of a complex submanifold and its applications
July 30 (Tue) at 16:00  18:10, 2019
Takayuki Koike (Lecturer, Department of Mathematics, Graduate School of Science, Osaka City University)
Plan of the seminar: we separate each talk into two. In the first 60 minutes the speaker gives an introductory talk for nonmathematicians. 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. Abstract: We explain our recent study on the complex analytic structure of a small tubular neighborhood of a complex submanifold, which is based on T. Ueda's classification theory. We also explain how to apply them to: (i) a study on (non) existence of a smooth Hermitian metric on a nef line bundle over a projective manifold with semipositive curvature, and (ii) a study on nonprojective and nonKummer K3 surfaces.
Venue: Seminar Room #160
Event Official Language: English

Introduction to magnitude of metric spaces
July 22 (Mon) at 13:00  15:00, 2019
Genki Ouchi (Special Postdoctoral Researcher, iTHEMS)
Leinster introduced the notion of magnitude of a metric space. It is a real number measuring the effective number of points in a metric space. In this talk, I will review generalizations of metric spaces (e.g. asymmetric metric spaces). After that, I would like to talk about the definition, examples and fundamental properties of magnitude.
Venue: Seminar Room #160
Event Official Language: English

Introduction to Schroedinger Operators
July 12 (Fri) at 16:00  18:10, 2019
Keita Mikami (Research Scientist, iTHEMS)
Plan of the seminar: we separate each talk into two. In the first 60 minutes the speaker gives an introductory talk for nonmathematicians. 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. Abstract: In this seminar, I will talk about mathematical study of Schroedinger operators (or Schroedinger equation). Part 1: I will talk about what mathematicians do to find a solution to Schroedinger equation. The goal of the first part is to be able to check the existence of solutions of Schroedinger equations in terms of decay/growth rate of potentials. Part 2: I will talk about what can we say about solutions to Schroedinger equation constructed in the first part. Especially, the relationship to the corresponding classical mechanic is introduced.
Venue: Seminar Room #160
Event Official Language: English

Seminar
Large scale dynamics of integrable systems
July 12 (Fri) at 16:00  17:00, 2019
Takato Yoshimura (King's college London, UK)
Hydrodynamics has been a universal tool to study the large scale (longwavelength) dynamics of interacting manybody systems. It had not been, however, applied to integrable systems until 2016 when two papers, one of which is ours [Physical Review X 6 (4), 041065, (2016)], provided a first legitimate hydrodynamic theory of integrable systems that incorporates the anomalous number of conserved quantities in those systems. The key idea of the theory rests upon the use of thermodynamic Bethe ansatz that allows us to express the essential ingredients in hydrodynamics, densities and currents average of conserved charges, in terms of the quasiparticle basis. In this talk I will review this new hydrodynamic theory, coined generalized hydrodynamics (GHD). I will first introduce the basics of GHD, highlighting the difference with the conventional hydrodynamics (i.e. hydrodynamics for nonintegrable systems). I will then present some recent developments in the theory, such as the exact computation of the Drude weight and hydrodynamic correlation functions.
Venue: Building 14 #213, Yagami campus, Keio University
Event Official Language: English

Seminar
ABBL/iTHEMS/rEMU Joint Seminar: Towards systematic and consistent nuclear data inputs for astrophysical rprocess with Bayesian approaches
June 28 (Fri) at 14:00  15:00, 2019
Haozhao Liang (Senior Research Scientist, Quantum Hadron Physics Laboratory, RIKEN Nishina Center for AcceleratorBased Science (RNC))
This is his 2nd seminar talk for nonexperts of nuclear physics, following the 1st one on 18th Jan. 2019. Abstract: In this interdisciplinary talk, I will start with some basic concepts as well as some frontiers of nuclear physics, and then introduce the roles of nuclear data inputs for the study of astrophysical rapid neutroncapture process (rprocess), which is responsible for the creation of approximately half the abundances of the atomic nuclei heavier than iron. Recent progress in nuclear physics focuses on improving the accuracy of crucial nuclear inputs, such as nuclear masses, betadecay halflives. Nevertheless, in most of the studies these inputs are investigated individually. One of our ongoing attempts is to organize the crucial nuclear inputs in a systematic and consistent way, together with Bayesian and/or machine learning approaches, which are able to provide not only the theoretical results but also the corresponding uncertainties.
Venue: 224226, Main Research Building
Event Official Language: English

Asymmetric metric and coarse geometry
June 20 (Thu) at 16:00  18:10, 2019
Hiroki Kodama (Visiting Scientist, iTHEMS / Assistant Professor, Advanced Institute for Materials Research (AIMR), Tohoku University)
Plan of the seminar: we separate each talk into two. In the first 60 minutes the speaker gives an introductory talk for nonmathematicians. 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. Abstract: For most of mathematicians, metric is symmetric. However, we can define asymmetric metric without any difficulty. "Coarse" is a notion to describe some large scale viewpoint. For example, the set of real numbers is coarse equivalent to the set of integers (with respect to standard metric). I will discuss asymmetric metric space in "coarse" sense. Part 1: I will define metric space and asymmetric metric space. I will also explain a notion of coarse equivalence. Part 2: I will discuss what kind of asymmetric metric space is not coarse equivalent to (symmetric) metric space. I also would like to give other generalizations of metric.
Venue: Seminar Room #160
Event Official Language: English

Seminar
Using combined ParticlesinMHDCells to model particle acceleration in astrophysical shocks
June 17 (Mon) at 14:00  15:00, 2019
Allard Jan van Marle (Research Professor, Ulsan National Institute of Science and Technology, Republic of Korea)
Astrophysical shocks can accelerate charged particles through diffusive shock acceleration. This process involves repeated shock crossings where the particle gains energy from collisions with the electromagnetic field. Eventually, these particles will reach relativistic speeds and can be observed as cosmic rays. In order to simulate this process, we need a method that can handle both the largescale structure of astrophysical shocks, as well as the behaviour of individual particles. We achieve this by combining the classical magnetohydrodynamics (MHD) and particleincell (PIC) methods. This allows us to describe the thermal plasma of the shock through MHD, while simultaneously using PIC to follow the movement of nonthermal particles as they are accelerated. Our results show a complicated interaction that destabilizes the shock, reducing the efficiency with which particles can be accelerated.
Venue: Seminar Room #132
Event Official Language: English
628 events
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