报告题目：Fractionalization and Anomalies in Symmetry-Enriched U(1) Gauge Theories
报告人：宁上强，2010-2014年就读于山东大学泰山学堂物理取向，并取得学士学位，2014年保送清华大学高等研究院，并于2019年取得博士学位，2019至今为香港大学物理系博士后。
就读于山东大学期间，积极参加科研训练相关活动，先后在王萌、戴瑛和郑雨军老师课题组学习参与科研活动。就读于清华大学期间，保持广泛视野，积极与国内国际的同行开展科研合作，先后访问香港中文大学、香港城市大学、麻省理工学院等高校，与斯坦福大学、加州理工大学、耶鲁大学和哈佛大学等单位同行展开研究合作和发表多篇学术文章，并在文小刚教授的指导下取得物理学博士学位。研究方向主要为量子多体系统的对称性和拓扑，对新奇物态(如量子磁性、拓扑超导、临界现象等), 特别是拓扑物态方面的基础问题(如刻画、分类、有效场论以及模型实现等)有浓厚兴趣。
报告内容：3+1D U(1) gauge theory is the effective field theory of a three-dimensional U(1) quantum spin liquid, which is an exotic gapless phase with emergent gapless photon and also gapped fractionalized electric charges and magnetic monopoles. In the presence of global symmetries, these fractionalized excitations can transform in different fractionalization patterns, which can be captured by projective representations of the symmetry group. Symmetry properties of these gapped excitations determine the universal properties of a symmetric U(1) quantum spin liquid, as well as the nature of its proximate phases. However, certain patterns of symmetry fractionalization cannot be realized in strictly 3+1D . Instead, they can only be realized on the boundary of 4+1D symmetry-protected topological phases. This type of symmetry fractionalization patterns are referred to as possessing 't Hooft anomalies. We obtain the classification of the patterns of symmetry fractionalization in symmetry-enriched U(1) gauge theories, and, in particular, an explicit formula to determine the relevant 't Hooft anomalies in terms of the fractionalization patterns.
Ref: Phys. Rev. Research 2, 043043 (2020)
报告题目：Driven-Dissipative Phase Transition in a Kerr Oscillator
报告人：张鑫，山东大学泰山学堂2011级毕业生，研究生就读于杜克大学，在Harold U. Baranger指导下取得博士学位，现为自由柏林大学博士后。研究兴趣为量子多体物理和量子光学。
报告内容：Due to interest in non-equilibrium physics and rapid advances of quantum simulation, quantum systems subject to dissipation, called open quantum systems, have attracted increasing attention. However, because of their additional complexity compared with traditional closed systems, open quantum many-body physics has been obscure. Here, we study open quantum many-body physics using a minimal model, namely a Kerr non-linear oscillator subject to driving and dissipation. Both numerical and analytical solutions are provided for this model. It contains surprisingly rich physics: a quantum phase transition, PT symmetry, critical scaling, and state squeezing. Because of the model's simplicity and solubility, it can serve as a paradigm for exploring open quantum many-body physics.
Ref: arXiv:2007.01422
本次活动采用线下线上相结合的模式，活动时间：2021年4月2日15：00至19：30，线下会议地点：山东大学老数学楼309，线上腾讯会议号：559207940。本次活动由泰山学堂13级毕业生、帝国理工大学博士赵宏政主持，会议邀请山东大学物理学院院长陈峰、山东大学物理学院郑雨军教授作特邀嘉宾。
