セミナー 2020年

Shoji Hashimoto, KEK

[EX] What is quark-hadron duality and how to overcome?

Online (Zoom) https://kds.kek.jp/event/36347/
Quark-hadron duality refers to an assumption that one can use perturbative QCD to compute a class of physical processes. Its associated uncertainty is hard to quantify, and even ignored in some cases, which may pose significant problem on the analysis of precise experimental data. We develop a formalism to get rid of this assumption and compute the physical processes fully non-perturbatively using lattice QCD. Examples are inclusive semileptonic decays of B meson and lepton-nucleon inelastic scattering cross section at low energy.

Sayantan Sharma, Institute of Mathematical Sciences

[QCD theory Seminar] Updates on Chiral plasma instabilities in gauge theory from lattice

Online (Zoom)
In this talk I will discuss about the latest understanding on chiral plasma instabilities and the onset of chiral turbulence in Abelian plasmas far from equilibrium. By performing classical lattice simulations of the microscopic theory, we show that the generation of strong helical magnetic fields from a helicity imbalance in the fermion sector proceeds through three distinct steps. During the initial stages the helicity imbalance of the fermion sector causes an exponential growth of magnetic field modes with right handed polarization. Secondary growth of unstable modes accelerates the helicity transfer from fermions to gauge fields and ultimately leads to the emergence of a self-similar scaling regime characteristic of decaying turbulence, where magnetic helicity is efficiently transferred to macroscopic length scales. In the turbulent regime the evolution of magnetic helicity spectrum can be described by an infrared power-spectrum with spectral exponent $¥kappa = 10.2¥pm 0.5$, which we determine from our simulations. I will conclude by discussing some expectations about this phenomenon in non-Abelian gauge theories.

Yutaka Matsuo, Tokyo University

Dimensional oxidization on coset space

Online (Zoom), indico page, slides (kek.jp only)
In the matrix model approaches of string/M theories, one starts from a generic symmetry gl(infty) to reproduce the space-time manifold.
In this talk, we propose the generalization in which the space-time manifold emerges from a gauge symmetry algebra which is not necessarily gl(infty).
We focus on the second nontrivial example after the toroidal compactification, the coset space G/H, and propose a specific infinite- dimensional symmetry which realizes the geometry.
It consists of the gauge-algebra valued functions on the coset and Lorentzian generator pairs associated with the isometry.
We show that the 0-dimensional gauge theory with the mass and Chern- Simons terms gives the gauge theory on the coset with scalar fields associated with H.

宮下精二, 日本物理学会, 東大物性研

[KEK連携コロキウム] 磁石への微視的モデルからのアプローチ −有限温度での保磁力解析−

Online (Zoom)

Yuto MInami, RCNP, Osaka University

Search for parity-violating physics in the polarisation of the cosmic microwave background, so called “Cosmic Birefringence”

Online (Zoom) https://kds.kek.jp/event/36423/
Polarised light of the cosmic microwave background, the remnant light of the Big Bang, is sensitive to parity-violating physics, cosmic birefringence. In this presentation we report on a new measurement of cosmic birefringence from polarisation data of the European Space Agency (ESA)’s Planck satellite. The statistical significance of the measured signal is 2.4 sigma. If confirmed with higher statistical significance in future, it would have important implications for the elusive nature of dark matter and dark energy.

Makiko Nio, RIKEN

[EX] On determination of the fine-structure constant: Electron g-2 and Atomic interferometers

Online (Zoom) https://kds.kek.jp/event/36346/
Any precision tests of the elementary particles are carried out on the assumption that the fine-structure constant alpha is sufficiently known.
Currently, there are two methods that provide equally accurate values of the alpha. One is the electron g-2 measurement together with its theoretical prediction from the QED theory. The other is the quotient of the Planck constant and the atomic mass (h/M) determined by using an atomic interferometer. I will report recent progress in both determination of the alpha including our own work on the five-loop QED calculation of the electron g-2.

Sinya Aoki, YITP

Conserved charges in gravity and entropy

Online (Zoom), indico page, slides (kek.jp only)
We propose a manifestly covariant definition of a conserved charge in gravity. We first define a charge density from the energy momentum tensor with a Killing vector, if exists in the system, and calculate the energy (and angular momentum) of the black hole by a volume integral. Our definition of energy leads to a correction of the known mass formula of a compact star, which includes the gravitational interaction energy and is shown to be 68% of the leading term in some case. Secondly we propose a new method to define a conserved charge in the absence of Killing vectors, and argue that the conserved charge can be regarded as entropy, by showing the 1st law of thermodynamic for a special case. We apply this new definition to the expanding universe, gravitational plane waves and the black hole. We discuss future directions of our research.

Yu Nakayama, Rikkyo University

[QCD theory Seminar] Anomalous hydrodynamics with dyonic charge

Online (Zoom)
We study anomalous hydrodynamics with a dyonic charge. We show that the local second law of thermodynamics constrains the structure of the anomaly in addition to the structure of the hydrodynamic constitutive equations. In particular, we show that not only the usual E ・ B term but also E^2 ? B^2 term should be present in the anomaly with a specific coefficient for the local entropy production to be positive definite.

Yasunori Lee, University of Tokyo

Revisiting Wess-Zumino-Witten terms

Online (Zoom), indico page, slides (kek.jp only)
We revisit various topological issues concerning 4d Wess-Zumino-Witten terms for SU and SO QCD, from the modern bordism point of view. We explain why the definition of the 4d WZW terms requires the spin structure, and also discuss how the mixed anomaly involving the 1-form symmetry of SO QCD is reproduced in the low-energy sigma model.

長谷川眞理子, 総合研究大学院大学

[KEK連携コロキウム] 少子化はなぜ起こるか 人間行動進化学からのアプローチ

Online (Zoom)
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