吉布斯采样、一阶相变、量子信息学、非相对论多尺度系统 | 本周物理讲座

1

报告人：Katsuya Hashino，Fukushima College

时间：3月11日（周二）10:30

单位：北京大学物理学院

地点：物理学院西楼B105

摘要：

In the Higgs potential of the standard model, it is known that the electroweak phase transition in the early universe is a crossover. However, the phase transition can occur as first-order when new physics effects contribute to the potential. lf the first-order phase transition took place in the early universe, the graitational waves are produced by bubble collision. Since theenergy of gravitational waves depend on the shape of the potential，it may be possible to explore the new physics effects in the potential through their observations. However, the spectrum of gravitational wave from first-order phase transition has some theoretical uncertainties. In this talk, we focus on some models beyond the standard model as an example, and discuss testaibility of them through the obseration of graitational wave. We take into account theoretical uncertainties, particularly those arising from renormalization group running effects, in the GW spectrum and discuss how precisely new physics effects can be probed.

报告人简介：

Katsuya Hashino received his Ph. D from University of Toyama in 2019, and is now an assistant professor at Fukushima College. He has worked at Osaka University, Peking University and Tokyo University of Science as a postdoc. His main interest is Higgs physics. Especially, he has focused on the dynamics of electroweak phase transitions in the eary Universe.

2

报告人：刘景铖，南京大学计算机学院

时间：3月11日（周二）12：00

单位：江苏省物理学会

链接：

摘要：

给定一个复杂系统的部分观察，如何高效地按照符合给定观察的条件分布进行模拟/采样？这样的计算采样问题在现代数据分析和机器学习中扮演着非常重要的角色，也有着理论物理学的背景。事实上，计算机科学中经典的约束求解问题，均对应着一个带复杂多体相互作用的粒子系统。因此计算机科学关心的约束求解问题中，解空间的整体几何性质的变化，也对应于物理系统中的相变现象。对于这些相变现象和采样算法的深入理论研究，不仅仅有助于回答“计算问题何时是困难的，何时是容易的”这样的基础科学问题，也在实践应用中证明了其价值。本报告将简单介绍这一研究方向，和一些我们已知的结果。

报告人简介：

刘景铖，南京大学计算机学院副教授，2019博士毕业于加州大学伯克利分校，导师是哥德尔奖得主Alistair Sinclair；毕业后在加州理工学院的计算与数学科学学院担任Wally Baer and Jeri Weiss讲席博士后。主要研究方向包括随机算法，计数与采样问题，计算相变理论和理论计算机科学，代表成果全部发表在STOC, FOCS, SODA和Journal of the ACM, SIAM Journal on Computing等国际一流的会议与期刊上；成果中两项分别入选差分隐私教材Hands-On Differential Privacy，和图灵奖得主Avi Wigderson编写的科普书籍《数学与计算》。入选国家青年高层次人才，主持国家自然科学基金面上项目。

3

报告人：Zhewei Yin，Northwestern University&Argonne National Laboratory

时间：3月11日（周二）14：00

单位：北京大学物理学院

地点：物理学院西楼B105

摘要：

The scattering amplitudes program aims to obtain observables from quantum field theory without cumbersome local formulations such as Feynman diagrams. A key step in this procedure is to determine the constraints satisfied by the on-shell amplitudes, according to the guiding principles of the theory in consideration. Recently a novel group of constraints originated from concepts in quantum information science has been increasingly drawing people's attention. I will first discuss the investigation on the amount of entanglement resulted in particle scattering, and reveal a universal correspondence between entanglement entropy and (semi)-inclusive cross sections. A careful formulation of wave packets for the initial states is essential in arriving at this relation. I will then discuss in the context of particle scattering the notion of magic, which quantifies the computational advantage of quantum states over classical algorithms. Research on this topic is still in its early stage, and can benefit both fundamental physics and quantum information science.

报告人简介：

Dr Zhewei Yin obtained his BSc degree in 2015 at Peking University, China, and his PhD degree in 2020 at Northwestern University, USA. He then became a postdoctoral researcher at Uppsala University, Sweden, after which he has been holding a joint appointment as a postdoctoral fellow at Northwestern University and Argonne National Laboratory, USA. He works in the field of theoretical high energy physics, with a focus on discovering new properties and developing modern methods in scattering amplitudes and effective field theories, as well as connecting these formal development to particle phenomenology, gravitational wave physics and quantum information science.

4

报告人：Hiroshi Shinaoka，Saitama University

时间：3月12日（周三）11:00

单位：中国科学院理论物理所

地点：北楼322

摘要：

Recently, quantics tensor trains (QTT) have been proposed as an efficient numerical tool for quantum field calculations. QTT can handle the coexistence of widely varying length, energy, and time scales while enabling fundamental operations such as Fourier transforms and convolutions in a compressed form.

In this seminar, I will give a blackboard-style talk on recent efforts to solve quantum field problems in the imaginary-time formalism, including the solution of parquet equations and multiorbital impurity models. For those unfamiliar with QTT, I will provide a brief introduction.

报告人简介：

Hiroshi Shinaoka is a computational physicist with a broad research scope, spanning from first-principles calculations of strongly correlated materials to the development and application of tensor network methods. Currently an Associate Professor at Saitama University, with a diverse academic background including international research experience at ETH Zurich. Actively involved in the development of open-source software and making significant contributions to computational physics and quantum material science.

5

报告人：Chenjie Wang，University of Hong Kong

时间：3月12日（周三）15:00

单位：北京大学物理学院

地点：物理楼，西563会议室

摘要：

I will discuss a construction of a family of 1D quantum lattice models that respect unitary fusion category symmetry. This family can be thought of as edge models of 2D symmetry-enriched topological states. An interesting feature of these models is that they often (but may not always) exhibit a gapless critical phase, i.e., a gapless region of codimension zero in the parameter space, due to the presence of fusion category symmetry. I will discuss numerical results of some examples.

报告人简介：

Chenjie Wang, Associate Professor at University of Hong Kong, graduated from University of Science and Technology of China in 2007 and obtained his PhD from Brown University in 2012. He has been working on transport in quantum Hall effects and theory of strongly correlated topological phases. His recent research interests include localization phenomenon and generalized symmetries in topological phases and quantum criticality.

6

报告人：Prof. Francisco J. Garcia-Vidal, Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Spain

时间：3月13日（周四）14:30

单位：北京大学物理学院

地点：物理学院中215会议室

摘要：

When the interaction between light and matter is strong enough, photon and matter excitations mix to create hybrid light/matter states called polaritons. Traditionally, their hybrid character has been used to achieve new functionalities in which polaritons are utilized as dressed photons. However, over the last ten years, it has become clear that the strong light-matter coupling regime can be used with an alternative purpose: to significantly modify material properties by dressing the matter excitations. Under strong coupling conditions, it has been shown that energy transport and harvesting in organic materials can be enhanced and that the energy landscape of the molecules can be altered in such a way that photochemical reactions and even ground-state chemical reactions can be modified. This new platform for creating quantum materials has triggered the search for achieving strong light-matter coupling conditions with other types of electronic excitations, such as those associated with excitons in van der Waals 2D materials and perovskite quantum dot solids, among others.

In this seminar I will present the main findings in this brand-new research field, but also our accompanying efforts in the last ten years to developing an accurate theoretical formalism, able to capture the complex and quantum nature of the electromagnetic fields associated with the nanophotonic structures in which polaritons emerge.

报告人简介：

Francisco J. Garcia-Vidal is a scientific group leader and full professor at the Physics department of the Autonomous University of Madrid (UAM) in Spain. Prof. Garcia-Vidal and his group have worked in different areas within Plasmonics and Metamaterials such as: surface enhanced Raman scattering, the phenomenon of extraordinary transmission of light and other waves through subwavelength apertures, the development of the concept of spoof surface plasmons and, more recently, Quantum Nanophotonics. Prof. Garcia-Vidal has authored around 300 refereed journal articles, which have received more than 48,000 citations (H-index: 103), and he has been included seven times in the list of Highly Cited Researchers in the field of Physics. He is also the founding director of the Condensed Matter Physics Center (IFIMAC) at UAM, and he was also the recipient of an ERC Advanced Grant (2012-2017) devoted to analysing quantum effects in Plasmonics. Prof. Garcia-Vidal is also a Fellow of the Optical Society of America and, from January 2018 to December 2021, served as a Divisional Associate Editor of Physical Review Letters. He was the recipient of the King Jaume I prize for Basic Research in year 2020, and he has been also awarded with the National prize of Physics in Spain in year 2021.

7

报告人：Nora Brambilla，慕尼黑工业大学

时间：3月13日（周四）15:00

单位：北京大学物理学院

链接：

摘要：

In this colloquium, we delve into the construction of a potential NREFT (pNREFT), a framework that directly tackles bound state dynamics reimagining quantum mechanics from field theory. Focusing on heavy quarkonia, pNRQCD facilitates systematic definitions and precise calculations for high-energy collider observables.

At the cutting edge, we investigate nonrelativistic bound states in intricate environments, like the newly discovered exotics X, Y, Z above the strong decay threshold and the behavior in out-of-equilibrium scenarios, such as quarkonium suppression in a Quark Gluon Plasma or dark matter interactions in the early universe. Our ability to achieve precision calculations and control strongly interacting systems is closely linked to bridging perturbative methods with nonperturbative tools, notably numerical lattice gauge theories.

报告人简介：

Nora Brambilla是粒子物理与核物理领域国际顶级专家学者。她的研究兴趣在于理论粒子与核物理；强相互作用物质；用于标准模型的有效场论、有限温度量子色动力学、夸克胶子等离子体、非平衡态物理学、格点量子色动力学以及非微扰技术。她的成名作是提出了pNREFT（势非相对论有效场论）理论，建立了用量子场论系统精确描述量子力学问题的桥梁。

2023 年获得欧洲研究理事会高级资助项目，项目名称为 “EFT-XYZ：利用有效场论理解并预测 XYZ 奇异强子的性质”。2012 年当选为美国物理学会会士，表彰其在重夸克-反夸克系统理论方面的贡献，包括新有效场论的发展，以及通过创立并领导夸克偶素工作组对夸克偶素物理学领域所做出的贡献。她创立了国际夸克偶素工作组（QWG，2002 年成立）和夸克禁闭系列会议（1994开始）。

8

报告人：Lixin Dai，香港大学

时间：3月13日（周四）15:30

单位：北京大学物理学院

地点：KIAA-auditorium

摘要：

Tidal disruption events (TDEs) are among the most fascinating astronomical phenomena, offering a unique probe into the properties of massive black holes and the nuclear environments of galaxies. In this talk, I will present results from theoretical calculations of the realistic rates of TDEs for both supermassive and intermediate-mass black holes. These results reveal how TDE rates depend on black hole mass, stellar dynamics, and galactic environments. I will also show state-of-the-art simulations of TDE accretion, outflows and emissions, demonstrating how these processes produce the diverse emission features we observe, including Bowen fluorescence lines. Finally, I will discuss the broader implications of TDEs for black hole growth, particularly in the early universe, and their role in shaping galactic evolution. By exploring these results, we can better understand the physics of TDEs and their critical role in the growth of black holes and the evolution of galaxies across cosmic time.

报告人简介：

Lixin Dai is an associate professor in the Department of Physics of the University of Hong Kong. Prof. Dai received her B.S. in Physics and Mathematics from the Hong Kong University of Science and Technology and her M.S. and Ph.D. in Physics from Stanford University. She was a joint postdoc fellow at the Yale University and University of Chile, and then a research associate at the University of Maryland. She joined the University of Copenhagen as an assistant professor before joining the University of Hong Kong. Her research interests are mainly in theoretical and computational high-energy and time-domain astrophysics, with a focus on black hole accretion disks and jets, tidal disruption events, and their connections to galaxies. She currently co-chairs the TDE & AGN science topical panel of the Einstein Probe Telescope.

封面图片来源：

更多报告信息：

《物理》50年精选文章