Hiroki Ohata, Kyoto University
Bosonized Schwinger model on a lattice
Online (Zoom) Bosonization, in which a fermionic model in 1 + 1 dimensions is transformed to an equivalent bosonic model, has been a powerful technique for the analytical study of many models. However, although the bosonized model is usually much simpler than the original model, obtaining the analytical exact solution is still very hard in some cases.
Bosonization, in which a fermionic model in 1 + 1 dimensions is transformed to an equivalent bosonic model, has been a powerful technique for the analytical study of many models. However, although the bosonized model is usually much simpler than the original model, obtaining the analytical exact solution is still very hard in some cases.
In this seminar, I present the lattice formulation of the bosonized Schwinger model, which enables us to study the model using the Monte Carlo method. This approach has several distinct advantages over the conventional one based on the original fermionic Lagrangian. First, the approach is unambiguously free from the fermion doubling problem.
Second, it is also free from the sign problem. Moreover, much more efficient configuration generation is possible. I demonstrate the validity of my formulation by showing my numerical results and discuss possible applications to other models.
Ref: H. Ohata, Monte Carlo study of Schwinger model without the sign
problem, arXiv:2303.05481 [hep-lat].
東島智, 量子科学技術研究開発機構
[金茶会] フュージョンエネルギーの早期実現に向けて、JT-60SA始動
J-PARC研究棟2階会議室 リモート会場：小林ホール https://www-conf.kek.jp/kincha/
https://www-conf.kek.jp/kincha/
QSTでは、フュージョン（核融合）エネルギーの早期実現に向け、研究開発を実施している。このうち、那珂研究所にある日欧の国際協力で進めるJT-60SAは、フランスに建設中の核融合実験炉ITERの支援研究、その次に発電を行う原型炉のための先端的な運転手法の開発、ITER実験を主導できる研究者・技術者の育成を目的としている。JT-60SAは、旧装置のJT-60Uの施設を最大限再利用するとともに、超伝導コイルなどの新規設備の製作を日欧で分担しており、2013年1月より組立てを開始し、2020年3月に装置が完成した。その後、全てのシステムが設計どおりに連携して機能するかを実証する統合試験運転を進めていたが、2021年3月、コイル通電試験中にコイル接続部での放電による損傷が発生したため、約２年間にわたる改良と試験を行ってきた。初プラズマの達成に必要な性能を確保できたため、今年5月30日より真空排気運転を開始し、統合試験運転を再
開（6月5日にプレス発表）、今年秋の初プラズマ達成を目指している。
講演では、最新のフュージョンエネルギーをめぐる話題とJT-60SAについて取り上げる。
Kazuya Mameda, Tokyo University of Science
[QCD theory seminar] Nonlinear chiral kinetic theory
Online (Zoom)
The chiral kinetic theory is a pivotal theoretical tool for the transport theory of massless degrees of freedom. Despite various developments, the usual framework contains only linear-order quantum corrections. In this talk, I will explain the formulation of the chiral kinetic theory with the nonlinear-order corrections. Also I will show several findings from this nonlinear chiral kinetic theory, such as nondissipative transport phenomena, a consistency with the Euler-Heisenberg effective theory and a potential issue on regularization.
Johannes Henn, Max-Planck-Institute for Physics)
Finite Scattering Amplitudes From Geometry
Hybrid On-site: Seminar room, Kenkyu honkan 3F Online: Zoom
Scattering amplitudes are key ingredients for cross sections relevant to collider physics. In the last decade, novel geometric ideas have emerged that hint at a completely different formulation of quantum field theory. For example, the Amplituhedron provides, via geometric means, the all-loop integrand of planar scattering amplitudes in maximally supersymmetric Yang-Mills theory. Unfortunately, dimensional regularization, used conventionally for integration, breaks the beautiful geometric picture. This motivates us in this talk to propose a ‘deformed’ Amplituhedron, which is well-defined in four dimensions. Leveraging four-dimensional integration techniques based on differential equations, we compute the four-particle amplitude up to two loops, as a function of the two deformation parameters. The latter can be interpreted as certain mass and energy variables. We observe simple behaviour in various physical limits of the parameters.
Yushi Mura, Osaka University
Electroweak baryogenesis via top-charm mixing
Hybrid On-site: Seminar room, Kenkyu honkan 3F Online: Zoom
Electroweak baryogenesis is a promising scenario to solve baryon asymmetry of the Universe, which is one of big mysteries of particle physics. I will discuss a scenario of electroweak baryogenesis in the two Higgs doublet model with quark flavor mixing. In general, off-diagonal components of quark Yukawa interactions with additional Higgs bosons are strongly constrained by the data for flavor changing neutral currents. However, top-charm quark mixing is not the case, so that a large off-diagonal element can be taken, which can contribute to generating baryon asymmetry of the universe. I will also discuss characteristic predictions for Kaon rare decays in the scenario of top-charm electroweak baryogenesis.
Shigehiro Yasui, Hiroshima U
[QCD theory seminar] Exotic hadrons with charm and bottom flavors: X, Y, Z, Pc, Tcc and hadron interaction
Online (Zoom)
Researches of exotic hadrons have been conducted for a long time since the discovery of quarks by Gell-Mann and Zweig. Recently, there have been many experimental reports on candidates for exotic hadrons with charm and bottom flavors since the discovery of X(3872). Exotic hadrons, whose internal structures are different from normal hadrons, ask us important questions about QCD. What kinds of hadrons should exist? What is the hadron dynamics? What is quark confinement? Those questions may be resolved by studying the properties of exotic hadrons, such as productions, mass spectroscopy and decays. My presentation is divided into two parts. In the former part, I introduce the basics of X, Y, Z, Pc (charm pentaquark), Tcc (double-charm tetraquark), and so on, and review recent experimental and theoretical progress on the study of them. In the latter part, I focus on the recent study with my collaborators for the hadron interaction between a heavy flavored hadron (anti-D meson and B meson) and a nucleon with respecting chiral symmetry and heavy-quark spin symmetry, and discuss the possible extension from exotic hadrons to heavy flavored nuclei as quark many-body systems. I welcome questions and comments from people who are not so familiar with exotic hadrons.
賀沢 秀人氏 (Ph.D., Google ソフトウェアエンジニア / 言語処理学会 理事)
[KEK連携コロキウム] 大規模言語モデルの舞台裏
Online (Zoom)
最近 ChatGPT に代表される大規模言語モデル (Large Language Model; LLM）が大きな話題となっている。LLM以前の自動対話システムでは、宅配便の配達問い合わせのようにあらかじめ決められた話題と目的のために応答を生成するのがやっとであり、しかもその応答も定型文の域を出ないものが多かった。それにたいしLLMは一見人間が応答しているのと区別がつかないやりとりを広範な話題について行うことができるため、様々な応用が期待されるとともに、その発展についていろいろな懸念も生じている。本講演では、LLMとは実際のところどういうものなのかその仕組みを解説するとともに、単なる印象論を越えてLLMについて冷静に議論をするための視点を提供する。
Michiru Niibo, Ochanomizu University
Updated Constraints and Future Prospects on Majoron Dark Matter
Online (Zoom)
Majorons are (pseudo-)Nambu-Goldstone bosons associated with lepton number symmetry breaking due to the Majorana mass term of neutrinos introduced in the seesaw mechanism. They are good dark matter candidates since their lifetime is suppressed by the lepton number breaking scale. We update constraints and discuss future prospects on majoron dark matter in the singlet majoron models based on neutrino, gamma-ray, and cosmic-ray telescopes in the mass region of MeV-10 TeV.
川勝康弘, JAXA
[金茶会] 火星衛星探査計画MMXと火星探査
小林ホール リモート会場：東海1号館116室 https://www-conf.kek.jp/kincha/
https://www-conf.kek.jp/kincha/
本講演では、火星探査を技術面から俯瞰すると共に、2024年度の打上げを目指し開発が進む火星衛星探査計画MMXの概要を紹介する。まず、火星探査の歴史を振り返りながら、探査方法が発展していく中で、どのように新しく高度な技術が獲得されてきたかを紹介する。そして、2020年代、火星探査の最前線においてMMXが果たす役割を押さえつつ、MMXの概要と技術を紹介する。
Diego Blas, UAB
Detecting (high frequency) gravitational waves in a box
Online (Zoom)
