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.
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] 第１回 火星衛星探査計画MMXと火星探査
小林ホ ール 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。
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。
https://www-conf.kek.jp/kincha/
Diego Blas, UAB
Detecting (high frequency) gravitational waves in a box
Online (Zoom)
In the presence of a background EM field, the passage of GWs generate different modes in EM cavities by either their effect on the background field or by interacting with the boundaries of the cavity. In this talk, I will describe this process in some detail and show that these set-ups provide some of the best bounds for GWs in the MHz-GHz band. I shall finish by briefly describing the way GWs interact with spin systems.
Thanaporn Sichanugrist, University of Tokyo
Detection of hidden photon dark matter using the direct excitation of transmon qubits
Hybrid On-site: Seminar room, Kenkyu honkan 3F Online: Zoom
We propose a novel dark matter detection method utilizing the excitation of superconducting transmon qubits. Assuming the hidden photon dark matter of a mass of O(10) µeV, the classical wave-matter oscillation induces an effective ac electric field via the small kinetic mixing with the ordinary photon. This serves as a coherent drive field for a qubit when it is resonant, evolving it from the ground state towards the first-excited state. We evaluate the rate of such evolution and observable excitations in the measurements, as well as the search sensitivity to the hidden photon dark matter. For a selected mass, one can reach ɛ~10^{-13}-10^{-12} (where ɛ is the kinetic mixing parameter of the hidden photon) with a few tens of seconds using a single standard transmon qubit. A simple extension to the frequency-tunable SQUID-based transmon enables the mass scan to cover the range of 4-40 µeV (1-10 GHz) within a reasonable length of run time. The scheme has great potential to extend the sensitivity towards various directions including being incorporated into the cavity-based haloscope experiments or the currently available multi-bit Noisy Intermediate-Scale Quantum (NISQ) computer machines.
Mustafa A. Amin, Rice University
A Spin on Wave Dark Matter
Hybrid On-site: Seminar room, Kenkyu honkan 3F Online: Zoom
What can we learn about the intrinsic spin of ultralight dark matter from astrophysical/cosmological observations (ie. whether it is a scalar=spin-0, vector=spin-1, or a tensor=spin-2 field)? Using analytic calculations and 3+1 dimensional simulations, I will argue that the imprint of intrinsic spin can be seen via (i) the initial density power spectrum, (ii) interference patterns in the density field inside dark matter halos, and through (iii) (polarized) solitons with macroscopic intrinsic spin. Based on features in the initial power spectrum, I will provide a bound on the dark matter mass > 10^(-18) eV for post-inflationary production. With increasing intrinsic spin, interference patterns in halos are reduced (and the inner shapes of halos modified) — which can be probed by lensing and dynamical heating of stars. Finally, after introducing polarized solitons, I will show that the time-scale of emergence of solitons (within halos) increases with increasing spin, and briefly discuss electromagnetic and gravitational wave signatures from such polarized solitons.
Muneto Nitta, Keio University
[QCD theory Seminar] How baryons appear in low-energy QCD: Domain-wall Skyrmion phase in strong magnetic fields
Online (Zoom)
Low-energy dynamics of QCD can be described by pion degrees of freedom in terms of the chiral perturbation theory(ChPT). A chiral soliton lattice(CSL), an array of solitons, is the ground state due to the chiral anomaly in the presence of a magnetic field larger than a certain critical value at finite density. Here, we show in a model-independent and fully analytic manner (at the leading order of ChPT) that the CSL phase transits to a {\it domain-wall Skyrmion phase} when the chemical potential is larger than the critical value \mu_c=16\pi f_{\pi}^2/3m_{\pi} \sim 1.03 GeV with the pion’s decay constant f_{\pi} and mass m_{\pi}, which can be regarded as the nuclear saturation density. There spontaneously appear stable two-dimensional Skyrmions or lumps on a soliton surface, which can be viewed as three-dimensional Skyrmions carrying even baryon numbers from the bulk despite no Skyrme term. They behave as superconducting rings with persistent currents due to a charged pion condensation, and areas of the rings’ interiors are quantized. This phase is in scope of future heavy-ion collider experiments. This talk is based on arXiv:2304.02940 [hep-ph] in collaboration with M. Eto and K. Nishimura.
Yusuke Taki, Kyoto University
Entropy in dS/CFT correspondence and its application
Hybrid On-site: Seminar room, Kenkyu honkan 3F Online: Zoom
In this talk, we focus on dS/CFT correspondence, which is a proposal for de Sitter (dS) holography analogous to AdS/CFT. This talk contains two recent works. First we consider an application of dS/CFT to evaluation of the semi-classical limit of wave function of universe. Through the procedure of analytic continuation in the CFT side corresponding to that from AdS to dS, we can find an interesting structure that only “allowable” geometries appear as saddle points of the gravitational path integral. Second, we discuss an extension of the holographic entanglement entropy formula in AdS/CFT toward dS/CFT. We propose that the holographic formula is formulated for a generalized notion of entanglement entropy, called pseudo entropy.
Maki Takeuchi, Kobe University
The Mystery of the Standard Model and the Extra-Dimensional Model
Hybrid On-site: Seminar room, Kenkyu honkan 3F Online: Zoom
