Csaba Csaki, Cornell University
Magnetic scattering: pairwise little group and pairwise helicity
Online (Zoom) https://kds.kek.jp/event/36580/
I discuss how to construct a Lorentz-invariant S-matrix for the scattering of electrically and magnetically charged particles. A key ingredient is a revision of our fundamental understanding of multi-particle representations of the Poincare group. Surprisingly, the asymptotic states for electric-magnetic scattering transform with an additional little group phase, associated with pairs of electrically and magnetically charged particles. I will discuss the general construction of such states. The resulting “pairwise helicity” is identified with the quantized “cross product” of charges e1 g2- e2 g1 for every charge-monopole pair, and represents the extra angular momentum stored in the asymptotic electromagnetic field. We define a new kind of pairwise spinor-helicity variable, which serves as an additional building block for electric-magnetic scattering amplitudes. We then construct the most general 3-point S-matrix elements, as well as the full partial wave decomposition for the 2 -> 2 fermion-monopole S-matrix. In particular, we derive the famous helicity flip in the lowest partial wave as a simple consequence of a generalized spin-helicity selection rule, as well as the full angular dependence for the higher partial waves. Our construction provides a significant new achievement for the on-shell program, succeeding where the Lagrangian description has so far failed.
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 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)
磁石、つまり永久磁石は身近な物質であり、モーターや記録媒体などの多くの機器で重要な役割を果たしている。その機構解明、高性能化に向けて盛んに研究が進められている。特にその温度依存性の解明は重要課題になっている。しかし、そこには現在の物理学の方法では取り扱いが困難な多くの興味深い問題を含まれている。この問題への我々の試みを紹介する。ここでは、現在最強の磁石であるNd2Fe14Bを取り上げる。磁石の重要な性質である有限温度での保磁力は、通常の熱力学諸量とはちがい、理論的な定式化がない。この問題は準安定状態の緩和の問題であり、その崩壊はいわゆるスピノーダル過程とみなされるが、短距離力相互作用系では核生成過程のため、真の意味での特異性を持たない。そのため、見かけ上のスピノーダル過程を定式化しなくてはならないという困難な問題がある。この問題に対し、有限温度LLG方程式の方法や、Wang-Landau法を用いたモンテカルロ法によって、ナノサイズ粒子での保磁力の温度依存性を定量的に評価した。さらに、双極子相互作用のため多磁区構造が現れる大きなグレインでの保磁力機構についても解析した。最後に、磁石は、グレインの集合体であり、その集団としての保磁力機構の解析の試みについても触れたい。
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.
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)
