*2019年 [#le173fee] ***[[Seminar]] [#b85254f3] 日時: August 27 (Tue.) 15:00-16:00 場所: Meeting room A at CCS 講演者: Kazuki Hasebe (National Institute of Technology, Sendai College) タイトル: TBA 概要: TBA -[http://www-het.ph.tsukuba.ac.jp/Seminar/tsukuba-only/2019/seminar20190827_Hasebe.pdf 2019/8/27:slides(pdf)] 日時: July 16 (Tue.) 14:00-15:00 場所: D413 講演者: Yoshio Kikukawa (Univ. of Tokyo) タイトル: Gauge-invariant path integral measure for the overlap Weyl fermions in 16 of SO(10) 概要: We consider the lattice formulation of SO(10) chiral gauge theory with left-handed Weyl fermions in the sixteen dimensional spinor representation (16) within the framework of the Overlap fermion/the Ginsparg-Wilson relation. We define a manifestly gauge-invariant path-integral measure for the left-handed Weyl field using all the components of the Dirac field, but the right-handed part of which is just saturated completely by inserting a suitable product of the SO(10)-invariant 't Hooft vertices in terms of the right-handed field. We also discuss the relations of our formulation to other approaches/proposals to decouple the species-doubling/mirror degrees of freedom. Those include Eichten-Preskill model, Ginsparg-Wilson Mirror- fermion model, Domain wall fermion model with the boundary Eichten-Preskill term, 4D Topological Insulator/Superconductor with gapped boundary phase, and the recent studies on the PMS phase/"Mass without symmetry breaking". We clarify the similarity and the difference in technical detail and show that our proposal is a well-defined and unified testing ground for that basic question. -[http://www-het.ph.tsukuba.ac.jp/Seminar/tsukuba-only/2019/seminar20190716_Kikukawa.pdf 2019/7/16:slides(pdf)] 日時: July 10 (Wed.) 14:00-15:00 場所: D413 講演者: Yoshio Kikukawa (Univ. of Tokyo) タイトル: Why is the mission imposible? — Decoupling the mirror Ginsparg-Wilson fermions in the lattice models for two-dimensional abelian chiral gauge theories 概要: It is known that the four- and two-dimensional abelian chiral gauge theories of an anomaly free set of Weyl fermions can be formulated on the lattice preserving the exact gauge invariance. However, in the mirror fermion approach with Ginsparg-Wilson fermions, it was argued by Poppitz et al. that the mirror fermions do not decouple : in the 3450 model with Dirac- and Majorana-Yukawa couplings to XY-spin field, the two-point vertex function of the (external) gauge field in the mirror sector shows a singular non-local behavior in the PMS phase. We re-examine why the attempt seems a "Mission: Impossible" in the 345 model. -[http://www-het.ph.tsukuba.ac.jp/Seminar/tsukuba-only/2019/seminar20190710_Kikukawa.pdf 2019/7/10:slides(pdf)] 日時: July 3 (Wed.) 15:00-16:00 場所: Workshop room at CCS 講演者: Masaki Honda (Waseda Univ.) タイトル: 行列模型に基づく背景磁場付き非可換トーラス上の湯川結合 概要: 行列模型は超弦理論の非摂動的な定式化の候補の1つとして注目されている。 本講演では、行列模型の1つであるIKKT模型に基づき、背景磁場付き非可換トーラス上での湯川結合を計算した結果を示す。 初めに、IKKT模型と、この模型における非可換トーラスの実現方法を紹介する。 次に、比較のために、通常のトーラス上に背景磁場を入れた場合のレビューを行う。 続いて非可換トーラス上のDirac作用素およびゲージ場を導入する。 最後に、ゼロモード方程式をどのように解いたかを紹介し、その解を元に湯川結合の計算した結果を示す。 -[http://www-het.ph.tsukuba.ac.jp/Seminar/tsukuba-only/2019/seminar20190703_Honda.pdf 2019/7/3:slides(pdf)] 日時: June 28 (Fri.) 14:00-15:00 場所: Workshop room at CCS 講演者: Oliver Baer (Humboldt University Berlin) タイトル: Nucleon-pion-state contamination in lattice calculations of nucleon axial and pseudoscalar form factors 概要: The nucleon-pion-state contributions to QCD two- and three-point functions used in lattice calculations of nucleon form factors are studied in chiral perturbation theory. For physically small quark masses the nucleon-pion states are expected to dominate the excited-state contamination at large euclidean time separations. To leading order in chiral perturbation theory the results depend on two experimentally well-known low-energy constants only and the nucleon-pion-state contribution can be reliably estimated. Most severe is the nucleon-pion-state contribution to the induced pseudo- scalar form factor $\tilde{G}_P(Q^2)$, which shows a rather strong dependence of $Q^2$ and leads to a 20%-40% underestimation at small momentum transfer. This underestimation is also responsible for the violation of the generalized Goldberger-Treiman relation by the lattice form factors. The prospects for using the ChPT results to analytically remove the nucleon-pion-state contributions from the lattice data are discussed. -[http://www-het.ph.tsukuba.ac.jp/Seminar/tsukuba-only/2019/seminar20190628_Baer.pdf 2019/6/28:slides(pdf)] 日時: June 27 (Thu.) 15:00-16:00 場所: Meeting room A at CCS 講演者: Toshifumi Noumi (Kobe Univ.) タイトル: Conformal correlators in momentum space and cosmological applications 概要: Recent studies in cosmology have shown that analytic properties of inflationary correlators, together with approximate conformal symmetry realized at the end of inflation, are crucial for probing new physics at the inflation scale. These cosmological applications have then boosted research activities on conformal correlators in momentum space. In this talk, after introducing motivations from the cosmology side, I will discuss analytic properties and symmetry constraints on conformal correlators in momentum space. In particular, I will discuss how to construct a crossing symmetric basis of four-point functions based on consistent factorization in analogy with scattering amplitudes. -[http://www-het.ph.tsukuba.ac.jp/Seminar/tsukuba-only/2019/seminar20190627_Noumi.pdf 2019/6/27:slides(pdf)] 日時: May 15 (Wed.) 15:00-16:00 場所: D413 講演者: Kotaro Tamaoka (YITP) タイトル: A Generalization of the Entanglement Entropy and Holography 概要: We define a new information theoretic quantity called odd entanglement entropy (OEE) which enables us to compute the entanglement wedge cross section in holographic CFTs. The entanglement wedge cross section has been introduced as a minimal cross section of the entanglement wedge, a natural generalization of the Ryu-Takayanagi surface. First, we review basic ingredients in order to define the OEE. Then, we will explain some basic properties of the OEE. Finally, we explicitly compute the generalized entropy for mixed states in two-dimensional holographic CFT and see agreement with the entanglement wedge cross section. This talk is based on 1809.09109 (Phys. Rev. Lett. 122, 141601). -[http://www-het.ph.tsukuba.ac.jp/Seminar/tsukuba-only/2019/seminar20190515_Tamaoka.pdf 2019/5/15:slides(pdf)] 日時: April 11 (Thr.) 15:00-16:00 場所: Workshop room at CCS 講演者: Sato Yuki (Nagoya Univ.) タイトル: How to "cool down" Ising model on 2d dynamical triangulations 概要: The Ising model on 2d dynamical triangulations was originally introduced by Kazakov in 1986, which is a statistical system including gravitational degrees of freedom. This system is known to be critical at the finite temperature and the continuum theory defined around the critical point is the 2d gravity minimally coupled to fermions. We introduce an external parameter to the system, aiming at observing the quantum critical behavior. Tuning the parameter to a certain value the critical temperature reaches absolute zero and the resulting continuum theory at the zero temperature is NOT the 2d gravity minimally coupled to fermions. As it turns out, physics at the zero-temperature may differ depending on the "cool down speed". The talk will be based on the work with Tomo Tanaka (Phys.Rev. D98 (2018) no.2, 026026) and the work in progress with Jan Ambjorn. -[http://www-het.ph.tsukuba.ac.jp/Seminar/tsukuba-only/2019/seminar20190411_Sato.pdf 2019/4/11:slides(pdf)]