我们为什么需要建造一个“超级tau-粲工厂”？| 本周物理学讲座
报告人：郑阳恒，中国科学院大学
时间：4月4日（周四）16:00
单位：清华大学
地点：理科楼郑裕彤讲堂
粒子物理的标准模型已经非常成熟，其中QCD理论在高能量下的“渐进自由”性质也已被大量实验所证实，但在高能向低能过渡的能区，以及低能区的QCD理论则预研能力不足，需要进一步的发展且需要被实验检验。此外，现有的标准模型理论并不能完全解释宇宙中观测到的正反物质的不对称性，需要高精度实验测量，寻找超出标准模型的新的CP破缺来源。为了挑战这些基本问题，我们建议建造一个对撞质心系能量为2至7 GeV, 对撞亮度大于0.5×10^35cm^-2s^-1（比目前正在运行的北京正负电子对撞机BESIII实验高两个量级，且能量覆盖范围更宽）的超级tau轻子-粲强子工厂（STCF）。这将使得我国在BESIII实验结束后，继续在陶-粲能区物理领域以及低能强相互作用研究领域引领世界。报告人将重点介绍该实验装置上的物理研究亮点和相关建造上的技术挑战。
报告人：张潘，中科院理论物理所
时间：4月2日（周二）12:00
单位：中科院理论物理所
地点：理论所主楼322报告厅
如何准确地计算多粒子系统的自由能，热力学量，以及给出系统的无偏采样，是统计物理的核心问题之一。自上世纪初以来，统计物理学家建立了各种各样的理论和方法来处理此类问题，其中包括马尔科夫链蒙特卡洛，张量网络，重整化群，平均场近似及消息传递算法等等。在实际应用中，这些方法各有其优劣。 在这个报告中，张潘将介绍一种新的统计力学问题的计算方法---变分自回归神经网络(Variational Autoregressive Networks)。这个方法拓展了传统意义上的平均场方法，用自回归神经网络构建变分的概率分布，并通过强化学习的方法训练网络，进而可以同时计算系统的自由能上界，测量系统的能量，熵及各种热力学量，并直接无偏地对系统采样。 报告中张潘首先会从更广的角度描述统计物理的基本问题和机器学习中的非监督学习所具有的天然的联系，然后介绍变分自回归网络，如何利用它求解统计力学的基本问题，以及此方法在伊辛模型，自旋玻璃以及统计物理反问题中的应用。
3Optical spectroscopy study on high-performance photonic devices
报告人：刘新风，国家纳米研究中心
时间：4月2日（周二）15:00
单位：北京师范大学
地点：物理楼106
Unlike electronic devices, optical devices work with photons rather than electrons, which makes them 10-100 times faster. They are also more energy-efficient because of lower heat loss, better signal-to-noise ratios and less susceptible to the interference. For our researches, we do the optical studies of high-performance photonic devices by using spectroscopic means, including steady state absorption, photoluminescence (PL) and scattering, as well as time resolved PL and transient absorption. In this talk, I will firstly introduce the background of our optical spectroscopy study on photonic devices. Then, I will give the several examples of current work: 1) From micro-size photonic lasers to plasmonic lasers and the polaritonic lasers with perovksite as the gain material; 2) Charge carrier dynamics in the twist angle WSe2/MoS2 heterostructures; 3) Room temperature strong biexcitonic emission from CsPbBr3 nano-crystals by utilizing nonlinear plasmonic Fano effect. In the end, I will share some experiences and perspectives with the audiences.
报告人：张俊，中国科学院半导体研究所
时间：4月2日（周二）16:00
单位：北京师范大学
地点：物理楼106
电子-声子相互作用在固体物理中扮演非常重要的角色，例如在BCS超导理论中电子-声子配对形成的Cooper 对，材料的热力学性质，电子输运，光学性质等。在半导体材料中，电子-空穴由于库伦相互作用形成新的准粒子-激子，特别在低维半导体中，由于量子限制效应使得激子效应更为显著。在本报告中，主要介绍低维半导体中的激子-声子相互作用的探测和调控，如声子的边带拉曼冷却和加热、激子暗态和禁介声子态的耦合和探测、缺陷态和声子耦合等。
5高超声速飞行：发现与创造
报告人：姜宗林，中科院力学研究所
时间：4月2日（周二）19:00
单位：中国科学院大学
地点：玉泉路校区 礼堂
6Effective field theory approach to lepton number violation: dimension seven
报告人：Yi Liao，Nankai University
时间：4月3日（周三）10:00
单位：中科院高能物理研究所
地点：Seminar room 319, Theoretical Physics Division
Effective field theory offers an appropriate approach to lepton-number violating processes at low energy and to connecting to origin of lepton number violation at high energy scale. In this talk I'll focus on dimension seven operators appearing in standard model effective field theory. I'll discuss their completeness and independence, and their renormalization. I'll explain how to extract anomalous dimensions for a suitably chosen basis of operators constrained by nontrivial flavor relations. As simple illustrations, I'll estimate renormalization effects on neutrinoless double beta decay and unusual proton decay.
7Aspects on Entanglement Contour II: the holographic picture
报告人：Qiang Wen，Southeast University
时间：4月3日（周三）14:30
单位：中科院理论物理所
地点：Room 6420, ITP NEW BUILDING
I will discuss the fine structure in holographic entanglement entropy and its relation to entanglement contour. We consider a natural slicing of the entanglement wedge with the modular planes, which are two dimensional bulk surfaces tangent to the modular flow everywhere. This slicing gives a fine correspondence between the points in the boundary region and the points on the corresponding RT surface in the bulk. Together with our proposal for entanglement contour, we propose the correspondence between subsets on the RT surface and the boundary partial entanglement entropies, which can be considered as a refined version of the Ryu-Takayanagi (RT) formula. Also we show the partial entanglement entropy is invariant under the modular flow thus we can extract the modular flow from partial entanglement entropies.
8Topological Excitations in 1D and 2D Charge Density Wave Systems
报告人：Han Woong Yeom
时间：4月3日（周三）16:00
单位：北京大学
地点：Room W563, Physics Building, Peking University
Topological excitations or domain walls in magnetic, ferroelectric, multiferroic, and charge density wave (CDW) materials have played multiply important roles for various fundamental and technological issues. In this talk, we will review our recent research activity for atomic scale observation and manipulation of topological excitations in prototypical 1D and 2D CDW systems. In a 1D CDW system of indium atomic wires on silicon surfaces, we identified a new type (Z4) of soliton topological excitations, which can deliver and manipulate topologically protected quaternary-digit information. As a model system of complex 2D CDW systems, domain walls of the unique Mott-CDW insulating states of 1T-TaS2 are investigated extensively. In this system, domain walls have been related with emerging superconductivity and novel device applications. We discovered not only a method to manipulate domain walls in nanoscale but also well defined in-gap states within domain walls. These states are largely governed by strong electron correlation intrinsic to this material and structural reconstruction of domain walls, indicating multiple internal degrees of freedom within domain walls. A network of such domain walls, as formed in the nearly commensurate CDW phase, can host novel electronic states, which can explain the emergence of superconductivity generically. As a more conventional 2D CDW system, we focussed on 2H-NbSe2. Its CDW ground state has been known mysteriously as being incommensurate without a domain wall identified. We discovered a very unusual form of discommensuration in this material. All these results tell us the rich physics ?within? topological excitations, which in turn indicates the possibility of manipulating exotic quantum states through topological excitations in various 1D/2D systems.
报告人：Xin Wang
时间：4月4日（周四）10:00
单位：中科院物理研究所
地点：M236会议室
The first puzzle is a classical problem in microbiology dating back to Jacques Monod that bacteria grown on two carbon sources either consume both sources simultaneously or consume them sequentially. Here we use a metabolic network model of E. coli to show that optimal protein resource allocation and topological features of the metabolic network can quantitatively explain the choice of carbon acquisition. The second puzzle is an outstanding challenge in theoretical ecology named Competitive Exclusion Principle: the number of consumer species in steady coexistence cannot exceed that of resources. Here we show that by forming chasing triplets among the consumers and resources in the predation process, the Competitive Exclusion Principle can be naturally violated.
报告人：Bin Hu，BNU
时间：4月4日（周四）14:00
单位：清华大学
地点：蒙民伟科技南楼S727
Hale model is a fast semi-analytical modelling of the non-linear matter power spectrum. It is widely used in the covariance matrix computation in the standard LCDM model. In this talk, I will introduce our recent work on pushing this modelling to the generic dark energy model.
报告人：Tjonnie Li，The Chinese University of Hong Kong
时间：4月4日（周四）16:00
单位：北京大学
地点：KIAA-PKU Auditorium
Gravitational lensing phenomena are widespread in electromagnetic astrophysics, and in principle may also be uncovered with gravitational waves. I examine gravitational wave events in the limit of geometric optics, where one expects to see multiple signals from the same event with different arrival times and amplitudes, and wave optics, where one expects to see effects such as interference and diffraction.Recent studies are showing that second generation gravitational-wave detectors may observe more than one lensed event. I present the results from a search for signatures of gravitational lensing in the binary black hole events detected by Advanced LIGO and Virgo during their first two observational runs. In particular, we look for three effects: 1) evidence of lensing magnification in the individual signals due to galaxy lenses, 2) evidence of multiple images due to strong lensing by galaxies, 3) evidence of wave optics effects due to point-mass lenses. We find no compelling evidence of any of these signatures in the observed gravitational wave signals. Finally, I will also look ahead to the microlensing effects due to substructure on top of strong lensing by (clusters of) galaxies.
12储能技术概论
报告人：陈永翀，中科院电工研究所
时间：4月4日（周四）19:00
单位：中国科学院大学
地点：雁栖湖校区 教1-109
更多报告信息：中国物理学会期刊网学术讲座列表
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