软物质体系的熵调控策略-计算设计与理论模拟 | 本周物理学讲座

来源：中国物理学会期刊网

1软物质体系的熵调控策略-计算设计与理论模拟

报告人：燕立唐，清华大学

时间：6月29日（周六）16:00

单位：中科院理论物理所

地点：ITP South Building 6420

各向异性粒子(包括双亲性Janus粒子和Patchy粒子等)由于其表面性质和形状特征的非对称性而展现出极强的界面活化能力，在构筑界面组装结构及设计新型功能材料方面有着广阔的应用前景。从不同层次、不同尺度研究和理解大分子及其各向异性粒子在界面处不同相互作用的协同机制和结构形成及演变动力学，预报并优化对应的性能和功能，是此类新型组装基元走向实际应用亟待解决的关键科学问题之一。近年来，我们课题组通过建立和发展多尺度模拟模型并综合理论分析，着重研究了各向异性粒子在软物质体系(聚合物和生物膜等)界面上的作用、组装与动力学行为。本报告将重点汇报我们课题组在如下三个方面的理论模拟研究中所取得的最新进展: 1) 各向异性粒子界面自组装的熵驱有序调控策略；2) 复杂体系的熵驱界面调控及性能的多尺度模型及预报；3) 各向异性粒子在细胞膜界面的作用状态及动力学。

2Astrophysical applications of star cluster dynamics

报告人：Jongsuk Hong，KIAA

单位：北京大学
时间：6月25日（周二）12:00

地点：KIAA 1st meeting room

Star clusters are composed of a large number of stars bounded by their self-gravity. Different kind of clusters, such as open clusters, globular clusters (GCs), young massive clusters (YMCs), nuclear clusters, are classified according to their mass, age, central density, concentration and their environments, etc. Star clusters are usually considered ideal systems to study stellar evolution since stars in clusters have been assumed to be coeval and share the same chemical properties. Thanks to the recent development of computational resources, it is now able to simulate realistic systems to understand the dynamical history behind observed star clusters. In this talk, I will present recent works that I have done here in KIAA. I will mainly cover two topics. One is the interpretation of multiple populations, which is recently found in some YMCs in the Magellanic Clouds. I tested two possible scenarios (ad hoc formation and merger scenarios) numerically to check how either scenario is likely. I will also discuss how two different scenarios produce different kinematic fingerprints. The other topic is binary black holes (BBH) from GCs as gravitational wave sources. Especially I will focus on the correlation between the production of gravitational wave BBHs and their host GCs' properties like mass, size, binary fractions. I will provide analytic expressions for the dependence of the number of BBH mergers from individual GCs on the main cluster’s structural properties and the time evolution of the merger rates of these BBHs. These expressions provide an essential ingredient for a general framework allowing to estimate the merger rate density.

3气候怎么了？！

报告人：魏科，中国科学院大气物理研究所

时间：6月25日（周二）14:30

单位：中科院物理研究所

地点：M236会议室

全球变暖被认为是目前全球最大的环境问题，也是近几十年来最重要的国际议题之一，涉及到全球治理、产业升级、新旧能源转化等各个方面，影响及其深远。气候到底发生了什么变化？这次全球变暖有什么特征？是否会重塑我们的未来？本次讲座将介绍：全球气候变化的最新报告和监测结果，影响全球能量平衡的主要因子，气候变化的自然和人为活动因子，气候模式评估的不确定性，气候模式的发展等。由于气候变化所涉及到的产业、行业、领域和利益极其深远和复杂，本次讲座将主要讨论科学问题，希望能给听众在纷繁的观点之中提供判断的科学基础。

4嫦娥带你看月球——从弱信号提取到月球雷达探测

报告人：张金海，中国科学院地质与地球物理研究所

时间：6月25日（周二）15:30

单位：中科院物理研究所

地点：M236会议室

嫦娥奔月之后，她在月球上究竟看到了什么？又是如何看到的？本次报告将介绍我国嫦娥三号和四号的基本情况，涉及弱信号提取、测月雷达信号处理和高精度成像等相关的研究成果。

5Understanding the trends in the Bulge of the Milky Way

报告人：Victor Debattista，Univ. of Central Lancashire

时间：6月26日（周三）09:30

单位：清华大学

地点：蒙民伟科技南楼S727

I present a model that helps understand the trends of the Milky Way’s bulge, including their age, kinematics, chemistry and distributions. I conclude that the bulge of the Milky Way formed largely in situ, whereas only about 1% of stars were accreted. I also demonstrate that there are hints that the MW bulge cannot be young.

6Field-induced neutral Fermi surface and QCD3-Chern-Simons quantum criticality in Kitaev materials

报告人：邹柳俊，哈佛大学

时间：6月26日（周三）10:00

单位：清华大学

地点：物理系理科楼C302

We perform both numerical and theoretical studies on the phase diagram of the Kitaev materials in the presence of a magnetic field. We find that a new quantum spin liquid state with neutral Fermi surfaces emerges at intermediate field strengths, between the regimes for the non-Abelian chiral spin liquid state and for the trivial polarized state. We discuss the exotic field-induced quantum phase transitions from this new state with neutral Fermi surfaces to its nearby phases. We also theoretically study the field-induced quantum phase transitions from the non-Abelian chiral spin liquid to the symmetry-broken zigzag phase and to the trivial polarized state. Utilizing the recently developed dualities of gauge theories, we find these transitions can be described by critical bosons or gapless fermions coupled to emergent non-Abelian gauge fields, and the critical theories are of the type of a QCD3-Chern-Simons theory. We propose that all these exotic quantum phase transitions can potentially be direct and continuous in the Kitaev materials, and we present sound evidence for this proposal. Therefore, besides being systems with intriguing quantum magnetism, Kitaev materials may also serve as table-top experimental platforms to study the interesting dynamics of emergent strongly interacting quarks and gluons in 2+1 dimensions. Finally, we address the experimental signatures of these phenomena.

7The optically thick rotating magnetic wind from a massive white dwarf merger product

报告人：Kazumi Kashiyama，University of Tokyo

时间：6月26日（周三）12:00

单位：北京大学

地点：1st meeting room, KIAA

8Quantum No-Hiding and No-Masking

报告人：ARUN KUMAR PATI，HARISH-CHANDRA INSTITUTE

时间：6月26日（周三）13:30

单位：中国科学院大学

地点：雁栖湖校区 教1-208 

9Wallpaper group symmetry protected topological phases in (2+1)D interacting fermionic system

报告人：张健豪，清华大学高等研究院

时间：6月27日（周四）10:30

单位：清华大学

地点：物理系理科楼C302

The classification symmetry protected topological (SPT) phases with on-site symmetry in the interacting fermionic systems with arbitrary dimensions are well established by a generalized group super-cohomology theory, but the space group counterpart's classification is still in a puzzle. In this talk, I will introduce the classification of interacting fermionic SPT phases with wallpaper group symmetries in (2+1)-dimensional system. Furthermore, with the obtained classification data, we discuss the recently proposed correspondence principle between crystalline topological phases and those with internal symmetries through the explicit lower-dimensional block-state decoration.

10Detection of the Circumgalactic Medium of Nearby Galaxies via Emission Lines

报告人：Huanian Zhang，Univ. of Arizona

时间：6月27日（周四）14:00

单位：清华大学

地点：蒙民伟科技南楼S727

Galaxies are surrounded by diffuse and extended gas, which is often called the circumgalactic medium (CGM) and is the least understood part of galactic ecosystems. The CGM harbors more than 60% of the total baryons in a galaxy, is both the reservoir of gas for subsequent star formation and the depository of chemically processed gas, energy, and angular momentum from feedback. Observations and simulations of the CGM suggest that it is a multi-phase medium characterized by rich dynamics and complex ionization states. The study of the CGM has so far generally come from absorption line studies of the spectra of distant objects, typically QSOs, whose lines of sight intersect lower redshift galaxy halos. However, such study is limited by statistics. Instead, I will describe a novel approach to study the CGM via emission lines, which allows for direct mapping of individual galaxies and a variety of results obtained.

11Formation of Surface Silver Nano-network Structures through Hot Electron Regulated Diffusion-limited Aggregation

报告人：楊志忠，臺灣大學光電所

时间：6月27日（周四）16:00

单位：北京大学

地点：物理学院中楼215

A surface Ag nano-network pattern is formed by first depositing Ag nanoparticles (NPs) on a conductive template, which has a certain defect structure, and then illuminating the Ag NPs with ultraviolet (UV) light in a moist environment. Such an Ag nano-network pattern consists of multiple connected Brownian trees (BTs), which are produced through the diffusion-limited aggregation (DLA) process. In the DLA process, diffuse Ag+ ions, which are generated by UV light illumination and dissolved by a thin adsorbed water layer on the surfaces of the Ag NPs and used GaN template, settle to form a BT through the combination with excited hot electrons migrating into the template from the Ag NPs. The lateral transport of hot electrons in the template is regulated by the distributions of threading dislocation and point defect cluster in the template, which eventually become the centers of BTs. The structure of a surface Ag nano-network can potentially serve as a transparent conductor.

12Merger and mass ejection of neutron-star binaries in numerical relativity

报告人：Masaru Shibata，Max-Planck-Institute

时间：6月27日（周四）16:00

单位：北京大学

地点：KIAA-PKU Auditorium

On August 17th, 2017, merger of binary neutron stars was observed for the first time by gravitational-wave and electromagnetic telescopes. Optical and infrared observations in particular agree broadly with the prediction by numerical relativity. From this April, advanced LIGO and VIRGO are in O3 observation and already had a few candidates of neutron-star mergers. We expect several more observations of neutron-star mergers (including black hole-neutron star merger). I will review our current understanding for neutron-star mergers and related mass ejection that are obtained by numerical relativity simulations and summarize predicted observational (optical and infrared) features.

13Production of X(3872) accompanied by a photon or pion

报告人：Liping He，Ohio State University

时间：6月28日（周五）10:00

单位：中科院理论物理所

地点：ITP South (New) Building 6420 

The discovery of dozens of unexpected exotic hadrons containing a heavy quark and its antiquark presents a major challenge to our understanding of QCD.  A consensus has not even been reached on the nature of the first one to be discovered:  the X(3872). The observation in its decay modes has not been effective in discriminating between different models. There may be aspects of the production of X(3872) that are more effective at discriminating between models than the decays of X(3872).  

14Dynamical evidence for a dark substructure in the Milky Way halo

报告人：Ana Bonaca，Harvard CfA

时间：6月28日（周五）12:00

单位：北京大学

地点：KIAA 1st meeting room

Stars escaping globular clusters form thin, long and kinematically-cold tidal streams. In pristine conditions, these streams have nearly uniform density, however, new Gaia observations of one such structure in the Milky Way halo have revealed a likely site of perturbation. The on-sky morphology suggests a recent, close encounter with a massive and dense perturber. Known baryonic objects are unlikely perturbers based on their orbital properties, but observations permit a low-mass dark-matter subhalo as a plausible candidate. This observation opens up the possibility that detailed observations of streams could measure the mass spectrum of dark-matter substructures and even identify individual substructures and their orbits in the Milky Way halo.

15Observation of interface charge accumulation due to Maxwell-Wagener effect and its impact on the performance of organic devices and molecular deformation

报告人：Mitsumasa Iwamoto，Tokyo Institute of Technology, Japan

时间：6月28日（周五）14:00

单位：中科院理论物理所

地点：ITP South Building 6420

Maxwell-Wagener effect accounts for charge accumulation at the interface between materials, and this fact is well utilized to analyze device characteristics, e.g., I-V characteristics. However the observation of charge accumulation is necessary to deeply understand the charge accumulation phenomena and to further develop the theory of carrier transport in organic device. In this presentation, first I briefly talk about the Maxwell-Wagner effect, and show how the transfer characteristics of organic field effect transistors devices is analyzed using a Maxwell-Wagner model. Then I will show that electric field optical second harmonic generation (EFISHG) measurement is available to directly observe charge accumulation phenomena at the device interface. As examples, carrier behaviors in pemtacene field effect transistors, organic light emit diodes (OLED), and organic memory devices are visualized. In this talk, particular attention is the behavior of charge carriers at the organic memory elements using PVDF. According to the turn-over of PVDF molecules in films, the charge behavior in organic memory devices is analyzed using EFISHG and charge modulation spectroscopy.  As an extension of the Maxwell-Wagener effect, vesicle deformation in solutions under the a.c. field is analyzed, and the effect of charge accumulation is discussed. Also the experiment to probe charge accumulation at the interface between sphere vesicles and solutions is also demonstrated, and I will show the experimental evidence of charge accumulation at the interface by EFISHG.

更多报告信息：中国物理学会期刊网学术讲座列表

1.大型强子对撞机上的实验进展

2.认识黑洞的首个直接“视觉”证据

3.现实中的“降维攻击”导致二维拓扑量子物态 | 文小刚点评

4.物理学的忧伤

5.特别二的物理学——节选自《物理学咬文嚼字》彩色四卷本全集

6.晶体几何系列之三：准晶是高维晶体投影的证明

7.物理学交流的语言

8.建好2年多了,FAST干了啥？

9.一场学习革命

10.周光召先生与开放的中科院理论物理所 | 贺周光召先生从事科学事业65周年