锂电储能、原子调控、共振理论、相对论量子场论 | 本周物理讲座

学术 2025-01-07 09:31 北京

1 Field theory of monitored, interacting fermion dynamics with charge conservation

报告人：郭浩宇，Cornell University

时间：1月7日（周二）10:00

单位：中国科学院物理研究所

地点：M830

摘要：

Measurement-induced phase transitions (MIPTs) in monitored quantum dynamics are non-equilibrium phase transitions between quantum-chaotic (volume-law entangled) and entanglement-suppressed, area-law phases. Here we reveal how monitored dynamics are situated within the framework of general far-from-equilibrium, quantum condensed-matter physics. Measurement-induced heating effects scramble the distribution function in generic (interacting) monitored fermion systems, and this enables a simplified symmetry-based description of the dynamics. We demonstrate the equivalence of the Keldysh technique with the conventional Statistical-Mechanics Model for circuits, resulting from a doubled Hilbert-space (Choi-Jamiolkowski) mapping. We illustrate this using the monitored dynamics of interacting fermions with a conserved charge, deriving a unified effective field theory that captures all phases and phase transitions. The non-interacting counterpart in 1D space only has an area-law phase, with no MIPT. This was explained via an effective non-linear sigma model replica field theory possessing a very large symmetry. We show that other phases and phase transitions emerge when the replica symmetry is reduced by interactions. The reduced symmetry combines a replica permutation symmetry and charge-conservation within each replica. The former and its spontaneous breaking govern the MIPT, which can be recognized via a separatrix in the renormalization group flow. The replica-resolved charge conservation dictates the ``charge-sharpening" transition between two kinds of dynamics, where the global charge information is either hidden or reconstructible from the measurements. The field theory explains why the charge-sharpening transition should occur only in the volume-law phase. Our framework provides a template for other classes of MIPTs and situates these within the arena of non-equilibrium condensed matter physics.

报告人简介：

Haoyu Guo is a Bethe postdoctoral fellow at Cornell University. He received his PhD from Harvard University under the supervision of Prof. Subir Sachdev, and his research focused on understanding non-Fermi liquids and thermal Hall effects in quantum materials. He spent his undergraduate at Peking University and MIT, where he worked with Prof. Leonid Levitov on the hydrodynamics of electron fluid. Recently, his interests expanded to understanding non-equilibrium quantum systems, with a focus on dynamical freezing in Floquet systems and measurement-induced phase transitions in monitored fermionic systems.

2 Cosmological Signatures of Neutrino Seesaw

报告人：韩成成，中山大学

时间：1月7日（周二）14:00

单位：中国科学院理论物理所

地点：北楼322

摘要：

The tiny neutrino masses are most naturally explained by the seesaw mechanism through singlet right-handed neutrinos, which can further explain the matter-antimatter asymmetry in the universe. We propose a new approach to study cosmological signatures of neutrino seesaw through the interaction between inflaton and right-handed neutrinos. After inflation the inflaton predominantly decays into right-handed neutrinos and its decay rate is modulated by the fluctuations of Higgs field which act as the source of curvature perturbations. We demonstrate that this modulation produces primordial non-Gaussian signatures, which can be measured by the forthcoming large-scale structure surveys. We find that these surveys have the potential to probe a large portion of the neutrino seesaw parameter space, opening up a new window for testing the high scale seesaw mechanism.

报告人简介：

韩成成，中山大学物理学院副教授、博士生导师。他2014年在理论物理所取得博士学位，之后分别在亚太理论物理中心(APCTP)、东京大学卡弗里数物连携宇宙研究机构(Kavli IPMU)、韩国高等研究院(KIAS)从事博士后研究。2020年入职中山大学任现职，并入选中山大学中青年杰出人才计划。2023年起受聘为亚太理论物理中心的协联研究员(APCTP fellow)。已在PRL, JHEP等杂志发表论文五十余篇，总引用两千余次。主要研究兴趣包括LHC上的新物理、粒子宇宙学、暗物质模型等。

3 Implications of recent observations on Horndeski gravity

报告人：Gen Ye，Leiden University

时间：1月7日（周二）14:00

单位：中国科学院理论物理所

Zoom Meeting ID: 860 1220 0416

Passcode: 342961

摘要：

The cosmic microwave background (CMB) is one of the most precise measurements ever made in cosmology. It is great success of LCDM to explain the observed CMB spectra with only six parameters. However, recent study of the cosmological tensions, especially that of early dark energy, reveals the fact that even CMB can accommodate beyond a LCDM dark component occupying up to 10% of the total energy budget during recombination when the CMB is generated. This opens up an important window of studying modified gravity before and near recombination. In this talk, I will discuss some of my recent findings about modified gravity, within the framework of scalar-tensor theories, in light of recent BAO, SNIa and CMB observations. I will show that modified gravity might play an important role in restoring concordance from the cosmological tensions.

报告人简介：

Dr. Ye got his Bachelor’s degree in 2018 and Ph.D. in 2022 under the supervision of Prof. Yun-Song Piao at the University of Chinese Academy of Sciences, then moved to Leiden University as a postdoctoral researcher. His research interest lies on probing the fundamental laws of physics with cosmological observations, with an emphasis on gravity and the cosmological tensions. He has discovered the possible connection between the Hubble tension, the anti-de Sitter vacuum and the axion of mass 10^-26 eV. He has also developed a novel way of observing early Universe physics through resonance in the gravitational wave background. His recent research uncovered evidence of modification to general relativity in the new cosmological observations, which might be the key to restoring cosmological concordance.

4 Lectures on the theory of resonances: Part 1

报告人：Christoph Hanhart，Forschungszentrum Jülich

时间：1月8日（周三）10:00、1月9日（周四）10:00

单位：中国科学院理论物理所

地点: 国科大中关村校区教学楼 S104

摘要：

In these lectures the concepts of S-matrix theory and their implications for a theoretically sound description of resonances are discussed. In particular I will explain the connection between causality and analyticity, the implications of unitarity for production reactions and scattering amplitudes and the concept of positivity. Finally I will explain under which conditions certain simplified descriptions are justified for individual resonances.

报告人简介：

Christoph Hanhart is the recipient of the PIFI Distinguished Scientist Award (2025). He studied physics in Bonn and Sydney. As a theoretical physicist he works on phenomena of the strong interaction at the boundary between nuclear and particle physics at the Jülich Research Centre and at the University of Bonn, where he also holds an extraordinary professorship. The current focus is on investigations of exotic hadron states. He is a member of the Particle Data Group (PDG) and received the Teaching Award of the University of Bonn in 2018.

5 Cooperation between Two Agents through a Negotiation Game

报告人：Izat Baybusinov，University of Fribourg

时间：1月8日（周三）10:30

单位：中国科学院理论物理所

地点: 北楼322

摘要：

In economic literature much emphasis is put into considering what are the most useful actions given a standard game. The game is defined by a set of utilities and the interest is to deduce what are the most useful action that an agent can take. Concepts like the Nash equilibrium arise where agents defend their own interests from the other's actions but from which no collaboration is possible. This is evident in the Prisoner dilemma game where agents’ best actions is to defect which results in a net loss for both parties.

Due to this problem we study how cooperation can arise in a game and, most importantly, how two agents can interact between themselves to reach a common agreement. This leads to the proposal of a simple two players game we call negotiation where two players can reach a common solution which has interesting properties. In this setting we observe that cooperation arises when there is information scarcity in the game which results in the people's willingness to compromise their own best choice.

6 原子调控非线性光学腔的磁滞特性

报告人：李健宁，东北师范大学

时间：1月8日（周三）14:00

单位：中国科学院物理研究所

地点：M楼253会议室

摘要：

对于驱动-耗散量子系统来说，主方程可以描述其动力学和稳态。其中稳态是由泵浦（能量输入）和耗散（能量损失）之间的竞争所主导的一种动态平衡。最近，非线性Kerr光学腔中动态光磁滞现象引起了人们的关注，它类似于磁性材料中的磁滞回线。本报告利用二能级原子来调控这一特性，并阐明调控背后的机制与Liouvillian间隙的行为相关。此外，通过平均场方法给出了调控的临界点并与数值结果进行了比较；同时分析原子的引入对光学腔带来的影响。

报告人简介：

李健宁博士于2020年6月获得东北师范大学学士学位，现就读于东北师范大学，导师为衣学喜教授。硕博连读期间，共发表学术论文8篇，其中第一作者5篇；两次获研究生国家奖学金以及优秀研究生称号。

7 One-loop reduction in the relativistic quantum field theories at finite temperature and/or finite density

报告人：张浩然，四川师范大学

时间：1月9日（周四） 9:30

单位：中国科学院理论物理所

地点：北楼202

摘要：

Scattering amplitudes encode the essential physical information of microscopic interactions and serve as the bridge between theoretical framework and experimental data in quantum field theories (QFTs). Feynman diagrams provide a standard method for calculating scattering amplitudes, and the calculation of one-loop Feynman diagrams is usually significant or even indispensable. Passarino-Veltman Reduction (PVR) can systematically and efficiently reduce the calculation of one-loop Feynman diagrams in relativistic QFTs, and is suitable for large-scale calculations of physical processes related to one-loop Feynman diagrams. The application prerequisite of PVR is that the system respects Lorentz symmetry, which requires not only relativistic energy-momentum relations but also zero temperature and zero density. In many practical problems, physical quantities depend on finite temperature and/or finite density, and finite temperature or finite density specifies a special inertial reference frame for measuring temperature or density, thereby destroying Lorentz symmetry and making PVR no longer applicable. In this talk, I will introduce generalized PVR that can reduce one-loop Feynman diagrams in relativistic QFTs at finite temperature and/or finite density. This reduction method can be applied to the study of physical properties in hot dense quark matter/nuclear matter.

报告人简介：

Hao-Ran Chang, is an associate professor of physics at Sichuan Normal University. He joined the Department of Physics at Sichuan Normal University after receiving his Ph.D. from the University of Science and Technology of China in 2012. He visited the Department of Physics at McGill University from 2017 to 2018. His research interests include the reduction of one-loop Feynman diagrams in finite-temperature field theory, and Higgs decays in particle physics, and collective excitations, optical conductivity, and magnetic interactions in condensed matter physics as well.

8 Critical Neural Avalanches Reconcile Response Reliability with Sensitivity for Optimal Neural Representation

报告人：周昌松，香港浸会大学

时间：1月9日（周四） 10:00

单位：中国科学院理论物理所

地点：北楼322

摘要：

Neural criticality has emerged as a unified framework that reconciles diverse multiscale neural dynamics such as the irregular firing of individual neurons, sparse synchrony in neural populations, and the emergence of scale-free avalanches. However, the functional role of neural criticality remains ambiguous. In particular, how highly sensitive and variable critical neural dynamics coexist with reliable neural representation is an unanswered question. In this study, we investigate the neural dynamics and representations in response to external signals in excitation–inhibition (E-I) balanced networks. Our findings reveal that, in contrast with the traditional critical branching model, the critical state of the balanced network simultaneously achieves maximal response sensitivity, maximal response reliability, and optimal representation of external signals. Moreover, we unveil a functional role of neural avalanches, which are not only a hallmark of criticality but also direct contributors to neural representation. By generalizing a semi-analytical mean-field theory, we demonstrate that heterogeneity in inhibitory connections is a mechanism underlying the heterogeneity of steady-state firing rates in the neural population, enabling the presence of signal-reliable neurons in reliable avalanches. Our study addresses a longstanding challenge concerning the functional significance of neural criticality -- the intricate coexistence of reliability and variability.

报告人简介：

周昌松，物理学博士，香港浸会大学物理系物理和复杂系统讲座教授，现任浸会大学非线性研究中心主任，计算及理论研究所所长，生命科学影像中心主任，曾任物理系系主任（2021-24）。1992年获南开大学物理学士，1997年获南开大学物理博士，1997-2007年在新加坡、香港、德国等地从事访问研究，是洪堡基金获得者。2007年加入香港浸会大学物理系，2011年获香港浸会大学“杰出青年研究者校长奖”，2021年获“杰出研究表现校长奖”，及香港研究资助局“高级研究学者奖” (2023）。周昌松博士致力于复杂系统动力学基础研究及其应用，特别是网络的复杂联结结构与体系的动态行为的关系和相互作用。近几年与国际国内系统和认知神经科学家合作，把这些理论进展应用到大脑的复杂联结结构和活动以及认知功能及障碍的分析和建模等方面研究中。周昌松博士对生物神经网络复杂结构、动力学及其低成本高效益如何启发类脑智能具有浓厚的兴趣。在国际交叉学术刊物PNAS，Nature Communications, Physical Review Letters，Physics Reports，National Science Review，J Neuroscience， NeuroImage，Cerebral Cortex，PLoS Computational Biology等发表论文170余篇 (Google Scholar引用19600余次，H-因子为54)。任Scientific Reports 编委，PLoS One，Cognitive Neurodynamics学术编辑，及多种国际期刊常任审稿人。

9 锂电储能：从锂离子到锂金属电池

报告人：谢佳，华中科技大学

时间：1月10日（周五）14:00

单位：中国科学院物理研究所

地点：M楼253会议室

摘要：

在全球能源结构深刻转型的关键时期，《“十四五”新型储能发展实施方案》清晰定位了新型储能作为构建新型电力系统的核心技术与基础装备的重要地位，对推动实现碳达峰、碳中和目标具有至关重要的战略意义。其中，锂电池储能技术已成为新型储能领域的佼佼者。截至2023年，我国锂电储能累计投运规模已突破33.6GW，占新型储能市场的97.3%，预计到2035年，装机容量将达600GW，市场规模超万亿元。与此同时，科研界与产业界正密切关注着锂金属电池这一前沿领域。通过将负极材料由传统的石墨升级为锂金属，并与高比容正极材料相结合，锂金属电池展现出超高的理论比能量，为储能技术的革命性突破开辟了新的路径。然而，无论是已大规模商业化的磷酸铁锂电池，还是仍处于研发攻坚阶段的锂金属电池，在面对日益增长的储能需求与多样化应用场景时，均面临着寿命延长、比能量提升及安全性强化等多重技术挑战。本报告将深入剖析锂离子电池与锂金属电池的发展现状与挑战，详细介绍课题组在该领域的研究进展，涵盖关键材料的创新、电极结构的优化设计、器件设计与应用等多个维度，旨在为高性能锂电储能技术的持续革新与发展贡献新的思路与方案。

报告人简介：

谢佳，华中科技大学电气与电子工程学院教授、博导，国家杰出青年基金获得者，国家高层次人才计划青年项目入选者，科技部重点研发计划和青年973项目首席科学家，英国皇家化学学会Fellow，先进电工材料与器件研究中心副主任。2002年和2008年在北京大学和斯坦福大学分别获学士和博士学位，曾任美国陶氏化学资深研究员、合肥国轩高科研究院院长。主要从事电化学储能研究，主持储能电池领域重点研发计划、青年973和联合基金重点等多个国家级项目，以第二完成人荣获国家科技进步二等奖，以第一完成人荣获新疆科技进步一等奖、中国电工技术学会科技进步一等奖和首届青年科技奖。以第一/通讯作者发表SCI论文200余篇，获专利授权100余项。担任《储能科学与技术》编委和Interdisciplinary Materials学术编辑。

10 叠层衍射成像研究进展

报告人：殳峰，The University of Sydney, Australia

时间：1月10日（周五）15:00

单位：中国科学院物理研究所

地点：M楼253会议室

摘要：

叠层衍射成像（Ptychography）是一种基于相干衍射数据的高分辨率计算成像技术，其通过扫描样品和记录重叠区域的衍射图样，结合先进的相位恢复算法，实现对样品结构的高精度重建。该技术突破了传统显微镜光学分辨率的限制，可用于揭示纳米尺度材料、半导体器件和生物样品的微观结构。本报告将简要介绍悉尼大学在叠层衍射成像领域的研究背景及最新科研进展。

报告人简介：

殳峰是悉尼大学电气与计算机工程学院副教授。他于2002年在上海交通大学获得信息与控制工程系学士学位，并在新加坡南洋理工大学和澳大利亚墨尔本大学分别获得电气与电子工程硕士及博士学位。在重返学术界之前，他曾在微电子行业（例如微电子研究所IMEC、全球领先的半导体设备供应商荷兰ASML）工作了十多年。他目前的研究兴趣包括先进量测与检测，超精密测量及运动控制及相关技术在先进材料和生命科学等领域的应用。

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