2019年†
日時: February 21 (Fri.) 15:00-16:00
場所: Meeting room C at CCS
講演者: Christopher Sachrajda (Southampton)
タイトル: K → ππ decays from lattice QCD
「修士論文内部審査」
日時: January 21 (Tue.) 15:00-16:30
場所: Meeting room A at CCS
Hiroyuki Adachi "The Berezin-Toeplitz quantization for the fuzzy torus with a magnetic flux"
Kaishu Saitou "弦理論のドジッター真空について"
Toru Hayama "標準模型有効理論におけるミューオン・電子転換過程の計算"
日時: December 24 (Tue.) 15:00-16:00
場所: Workshop room at CCS
講演者: Tamiaki Yoneya (JPS)
タイトル: Covariantized Matrix Theory
概要:TBA
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: 代数の拡張に関連した高次元非可換幾何とランダウの物理
概要:
数の体系は、実数、複素数から始まり、四元数、八元数、クリフォード代数のように拡張されていく。
この代数の拡張と高次元の非可換幾何球面、非可換双曲体の密接な関係について紹介する。
特にランダウ模型（磁場中の荷電粒子の模型）に基づいて、高次元非可換幾何がどのように物理的に実現しているか詳しくお話しする。
高次元の量子ホール効果（トポロジカル絶縁体）、南部幾何も簡潔に紹介し、場の理論、弦理論との関係性についても議論したい。
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.
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.
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。
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.
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.
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).
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.
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