Shinya Aoki, Yukawa Institute for Theoretical Physics, Kyoto University
On the definition of entanglement entropy in lattice gauge theories
We focus on the issue of proper definition of entanglement entropy in lattice gauge theories, and examine a naive definition where gauge invariant states are viewed as elements of an extended Hilbert space which contains gauge non-invariant states as well. Working in the extended Hilbert space, we can define entanglement entropy associated with an arbitrary subset of links, not only for abelian but also for non-abelian theories. We then derive the associated replica formula. We also discuss the issue of gauge invariance of the entanglement entropy.In the $Z_N$ gauge theories in arbitrary space dimensions, we show that all the standard properties of the entanglement entropy, e.g. the strong subadditivity, hold in our definition. We study the entanglement entropy for special states, including the topological states for the $Z_N$ gauge theories in arbitrary dimensions. We discuss relations of our definition to other proposals.
安井繁宏, 東工大
[近藤問題に関する連続セミナー] クォーク物質におけるQCD近藤効果
倉本義夫, KEK
[近藤問題に関する連続セミナー] 近藤効果の理論的意義と最近の発展
Anupam Mazumdar, Lancaster U
Understanding Gravity
I will discuss how gravity in ultraviolet and infrared can be understood in such a way that it can ameliorate some of the singularity problems of nature and also provide some hints to the pertinent question of cosmological constant.
Mauricio Romo, Kavli IPMU
Two-dimensional supersymmetric field theories with boundaries
I will discuss recent progress on a particular class of 2d supersymmetric field theories on the disk: N=(2,2) Witten’s gauged linear sigma models. These theories are closely related to string compactifications on Calabi-Yau 3-folds, and so, the results have not only physical but also interesting mathematical consequences.
I will discuss recent progress on a particular class of 2d supersymmetric field theories on the disk: N=(2,2) Witten’s gauged linear sigma models. These theories are closely related to string compactifications on Calabi-Yau 3-folds, and so, the results have not only physical but also interesting mathematical consequences.
Kunihito Ioka, KEK
[Cosmophysics seminar] The Origin of Cosmic-Ray Hardenings
We will discuss the implications and possible origin of cosmic-ray hardenings recently observed by the AMS-02 experiment.
References:
AMS-02 Collaboration, “AMS Days at CERN” and Latest Results, 15, April, 2015.
Ohira & Ioka, ApJ 729 (2011) L13
Ohira, Kawanaka & Ioka, in preparation
Yuya Tanizaki, RIKEN
Lefschetz thimble積分法とその物理的応用
Picard-Lefschetz理論の量子系への応用が最近見いだされ、特に符号問題に対する新しいアプローチとしても注目を集めている。符号問題は大まかに言えば振動積分の評価の難しさに起因しており、とくにモンテカルロ法のimportance samplingが破綻してしまう、という内容が lattice field theory の文脈で有名であるが、平均場近似にもこの病的な振る舞いが引き継がれてしまうことが知られている。
本セミナーでは、Picard-Lefschetz理論の基礎的な内容を説明し、これがなぜ符号問題に有用だと考えられているのかについて述べる。その後このアイディアを応用して、簡単な行列模型の相転移現象を調べることで、Lee-Yangの定理とこの手法の関係について説明する。また、最近この手法を用いれば平均場近似に引き継がれた符号問題が回避されることを発見したため、その進展についても発表したい。
Koji Ichikawa, IPMU
Current and Future dark matter constraints from dwarf spheroidal galaxies
One of the most promising way to detect dark matter is to look for its annihilation or decay products among cosmic-rays (indirect detection). Recently, more and more interesting results are reported from measurements of cosmic-rays such as gamma-rays, neutrinos, positrons, antiprotons, etc. In this talk, I will especially focus on gamma-ray search from dwarf spheroidal galaxies (dSphs). Though the dSphs is one of the best target for the indirect detection, there remains large uncertainty on the estimation of dark matter profile around the dSphs. I will show how the constraints fluctuate under conservative estimation of the profile and discuss the future prospect of the constraints.
Yasuaki Hikida, Rikyo U.
N=3 higher spin holography and Higgs phenomenon
Superstring theory includes a lot of massive higher spin excitations, and there would appear a higher spi gauge symmetry at the tensionless limit. Moreover, it has been expected that these states could be described by a broken phase of higher spin gauge theory. Recently, it becomes possible to discuss the realizations of the idea with the help of Vasiliev theory and AdS/CFT correspondence. In this talk, I will explain recent developments on the concrete relation between higher spin gauge theory and superstring theory by making use of AdS/CFT correspondence. In particular, I will focus on the AdS_3 case. Moreover, I will show that higher spin fields become massive due to the braking of higher spin symmetry using a simple example.
Sadakazu Haino, Institute of Physics, Academia Sinica
[Cosmophysics Seminar] The new results from Alpha Magnetic Spectrometer (AMS)
