从液晶显示到液晶生物膜的弹性理论 | 本周物理学术讲座

1从液晶显示到液晶生物膜的弹性理论 

报告人：欧阳钟灿 院士

时间：4月19日（周四）15:00

单位：中科院物理所

地点：M楼234报告厅  

从19世纪被发现，液晶长期被认为是实验室的好奇心与有限的实用价值的软物质。20世纪70年代，由于液晶显示（LCD）技术的发现，液晶现在已作为一个年盈利数十亿美元全球产业的基础。4个发明人G. Haiermeyer ，W.Helfrich，M. Schadt，与 T. P. Brody于2012年二月因发明液晶显示被授予有“工程诺贝尔奖之称”的美国工程院最高奖，德瑞珀奖。在1971年发明成为现代LCD产业的关键技术--扭曲向列相液晶器，W.Helfrich 1973年把研究转向一个困惑了人们100多年的生理问题，为什么红细胞在人体内总是旋转对称的双凹碟形。他把细胞膜看成液晶膜，从液晶弹性理论导出了生物膜的曲面弹性自由能，这个自由能的变分导出了描述细胞形状的曲面方程(Ou-Yang and Helfrich, 1987)。这次报告将汇报我们多年来用Helfrich液晶流体膜（FM）理论研究的一些进展，我们发现Helfrich FM理论不仅能给出红细胞的形状的精确解析解而且预言存在生成圆半径比为根号2的环面泡并很快被多个实验室观察确认。特别是，Helfrich模型还可以成功地应用于其他软物质的复杂形状构成的研究，如给出符合实验发现构成胆结石的胆固醇螺旋膜螺旋角解析公式，碳纳米螺旋管形成机理，肽纳米结构管状到球状的结构相变，以及病毒衣壳的二十面体的自组装等。由于Helfrich的生物膜理论的杰出贡献，2012年9月在波茨坦为他举行了80岁诞辰的学术研讨会，出席会议并做报告的Yoshi1nori Ohsumi于2016年因细胞自噬（这与细胞形状变形有关）获得2016年诺贝尔生物物理与医学奖。2012年12月在以色列特拉维夫大学，因液晶生物膜理论的贡献授予W.Helfrich塞克勒国际生物物理奖，作者被邀请在颁奖会上做介绍液晶生物膜理论报告，本次讲座内容大体基于这个报告。

2科研创新与独角兽

报告人：刘循序，北京创业公社投资发展有限公司

时间：4月18日（周三）14:00

单位：中科院物理所

地点：M楼234报告厅 

将与大家分享自己这么多年的工作经验与心得体会，并深入探讨全球独角兽企业的发展情况与行业分布、科研与创业的关系、创业的一些关键要素，以及科研成果的转化等话题。

3Scalar dark matter explanation of the DAMPE data in the minimal Left-Right symmetric model

报告人：曹俊杰，河南师范大学

时间：4月17日（周二）14:30

单位：中科院高能物理所

地点：Theoretical Physics Division, 319 

In the talk the speaker will discuss the implication of the 1.4 TeV peak observed by DAMPE experiment, and review the explanations of the peak in new physics models. In particular, he will focus on the left-right symmetric model, and point out that the model itself can predict the DM which annihilates dominantly into leptons, and consequently it is capable of explaining the peak in a rather natural way. Other theoretical issues, such as unitary constraints on the model and the two loop effects on the RGE running of the relevant couplings, are also discussed.

4Competing Supersolid and Haldane Insulating phases in the 1d extended Bose Hubbard model 

报告人： G. BATROUNI，Universite de Nice-Sophia Antipolis 

时间：4月17日（周二）15:30

单位：北京师范大学物理系

地点：物理楼106

 Competition between different ordered phases in strongly correlated systems can lead to the appearance of new exotic quantum phases. I will iscuss the phase diagram of the extended one-dimensional Bose Hubbard model. I use quantum Monte Carlo and density matrix renormalization group (DMRG) to show that this system exhibits first order, second order and Kosterlitz-Thouless quantum phase transitions. I map out the the ground state phase diagram and show the appearance of an exotic Haldane phase for a small range of parameters while CDW, Mott, superfluid and supersolid phases appear for a wide range of parameters. 

5Nonlinear decay and plasma heating by toroidal Alfven eigenmode

报告人：仇志勇，Zhejiang University

时间：4月18日（周三）9:00

单位：中科院物理所

地点：M楼253会议室

Nonlinear decay of toroidal Alfven eigenmode (TAE) into a geodesic acoustic mode (GAM) and a lower kinetic TAE (LKTAE) with the same toroidal/popoidal mode number is investigated due to its crucial implications on TAE nonlinear saturation, improved confinement, as well as energetic particle (EP) power channeling, including fusion-alpha power density to bulk thermal plasma heating. The parametric dispersion relation is derived and analyzed, and the parameter range for this process to occur and dominate over other mechanisms is discussed. The nonlinearly generated LKTAE and GAM can be dissipated via electron and ion Landau damping, respectively, leading to anomalous EP slowing down and channeling of EP power to thermal ion heating. The thermal plasma heating rates are also estimated. Furthermore, the nonlinearly generated GAM, as the finite frequency zonal flow, could contribute to regulating drift wave turbulence and consequently, improved confinem. 

6Dirac fermions and critical phenomena

报告人：Michael Scherer，University of Cologne

时间：4月18日（周三）10:30

单位：中科院物理所

地点：M楼830会议室

In my talk, I discuss effective models for Dirac fermions which emerge as quasi-particle excitations on the honeycomb lattice and many other condensed-matter systems. These Dirac fermions can undergo different types of quantum transitions which represent unconventional universality classes related to variants of the Gross-Neveu model. In particular, I present our perturbative renormalization group study at four-loop order. We applied the computed series for the critical exponents and their Pade approximants to several phase transitions of current interest: metal-insulator transitions of spin-1/2 and spinless fermions on the honeycomb lattice, emergent supersymmetric surface field theory in topological phases, as well as the disorder-induced quantum transition in Weyl semimetals. Comparison with the results of other analytical and numerical methods, i.e. quantum Monte Carlo simulations, the functional renormalization group and the conformal bootstrap approach, is discussed. Depending on time, I will also discuss functional RG results for the fermion-induced quantum critical points and emergent symmetries of compatible order parameters in Dirac systems. 

7 标准模型外新物理寻找   

报告人：刘海波，中科院高能所  

时间：4月18日（周三）13:30

单位：中国科学院大学

地点：雁栖湖校区教1-313    

8 5-brane webs for 5d N=1 G2 theories 

报告人：Sung-Soo Kim，University of Electronic Science and Technology of China 

时间：4月18日（周三）14:30

单位：中科院理论物理所

地点：Conference Room 6420  

5d superconformal field theories (SCFTs) have various string constructions, one of which is type IIB (p,q) 5-brane web, and the 5-brane web is a useful tool to study qualitative and quantitative aspects of 5d SCFTs. We discuss 5d N=1 theories of gauge groups SO(N) and Sp(N) which can be constructed using 5-brane webs with an O5-plane. In this talk, we propose topological vertex formalism with an O5-plane, which enables one to compute the Nekrasov partition functions for 5d theories of gauge groups SO(N) and Sp(N). As an example, we apply the formalism to 5d Sp(1) gauge theory with Nf=0 and 8 flavors. We further explore 5d brane constructions for 5d G2 gauge theories through the Higgsing of SO(7) gauge theory with a hypermultiplet in the spinor representation, and then compute their partition functions based on 5-brane webs, by utilizing the topological vertex method with an O5-plane. 

9Dirac fermions and critical phenomena

报告人：Michael Scherer,University of Cologne 

时间：4月18日（周三）10:30

单位：中科院物理所

地点：M830 

In my talk, I discuss effective models for Dirac fermions which emerge as quasi-particle excitations on the honeycomb lattice and many other condensed-matter systems. These Dirac fermions can undergo different types of quantum transitions which represent unconventional universality classes related to variants of the Gross-Neveu model. In particular, I present our perturbative renormalization group study at four-loop order. We applied the computed series for the critical exponents and their Pade approximants to several phase transitions of current interest: metal-insulator transitions of spin-1/2 and spinless fermions on the honeycomb lattice, emergent supersymmetric surface field theory in topological phases, as well as the disorder-induced quantum transition in Weyl semimetals. Comparison with the results of other analytical and numerical methods, i.e. quantum Monte Carlo simulations, the functional renormalization group and the conformal bootstrap approach, is discussed. Depending on time, I will also discuss functional RG results for the fermion-induced quantum critical points and emergent symmetries of compatible order parameters in Dirac systems.

10Numerical Evidence of Emergent Symmetry in Spin-1/2 Heisenberg Chain

报告人：Pranay Patil, Boston University 

时间：4月18日（周三）16:00

单位：中科院物理所

地点：M830 

The antiferromagnetic Heisenberg chain is expected to have an extended  symmetry, [SU(2)xSU(2)]/Z_2 , in the infrared limit, whose physical  interpretation is that the spin and dimer order parameters form the components of a common 4-dimensional vector. Here we numerically  investigate this emergent symmetry using quantum Monte Carlo simulations  of a modified Heisenberg chain (the J-Q model) in which the logarithmic  scaling corrections of the conventional Heisenberg chain can be avoided. We show how the two- and three-point spin and  dimer correlation functions approach their forms constrained by conformal field theory as the system size increases and numerically  confirm the expected effects of the extended symmetry on various correlation functions. This talk will be based on work presented in https://arxiv.org/abs/1803.02041. 

11冷冻电镜病毒三维重构研究 

报告人：刘红荣，湖南师范大学 

时间：4月19日（周四）10:30

单位：中科院理论物理所

地点： Main Building,Conference Room 322 

近年来冷冻电镜技术取得了质的飞跃，病毒三维重构在推动该技术的发展过程中起到了至关重要的作用。多数病毒颗粒由二十面体对称的衣壳和内部非二十面体对称的基因组及大量相关蛋白（对称失配结构）组成。病毒颗粒的高对称性促进了其三维重构分辨率的提高，然而对称失配及超大尺度又极大地限制了其结构研究。本次汇报将介绍我们在冷冻电镜病毒近原子分辨三维重构、二十面体病毒对称失配三维重构及超大尺度病毒颗粒重构等方面所做的工作。

12The scientific impact of the LAMOST on exoplanet research

报告人：Jiwei Xie，Nanjing Univ. 

时间：4月19日（周四）14：00

单位：清华大学物理系

地点： 蒙民伟科技南楼S727 

With the discoveries of thousands of planets, the Kepler mission has brought revolutions to the exoplanet researching field, which is advancing from studying individual exoplanets to characterizing planet populations. However, making any reliable statistical inference with a large Kepler planet sample is seriously limited by the lack of accurate stellar parameters for the majority of the targets. With 4000 fibers and 5 degrees of diameter field of view, the LAMOST is uniquely positioned to perform a systematic spectroscopic survey of Kepler target stars, forming a complete and unbiased sample to perform statistical inference on planet distribution and correlations with host properties, which provides new insights on planet formation and evolution. This talk will review several such statistical studies, showing how LAMOST can impact the study Kepler planets. In the future, LAMOST will continue to play such a crucial role in the TESS era. 

13Multi-qubit superconducting quantum circuits 

报告人：王浩华, 浙江大学 

时间：4月19日（周四）16:00

单位：清华大学物理系

地点： 理科楼郑裕彤讲堂

In this talk, I will review our recent activities with our collaborators on designing and fabricating superconducting circuits integrating up to 20 qubits for scalable quantum information processing. In particular, I will introduce a superconducting quantum processor featuring 10 individually-accessible Xmon qubits that are controllably coupled to a bus resonator, based on which we deterministically produce the Greenberger-Horne-Zeilinger (GHZ) states with up to 10 qubits. The 10-qubit GHZ state, whose full information is obtained through tomographic measurement, represents the largest entangled state produced so far in solid state architectures. With the excellent control developed in our experiment, our multi-qubit superconducting circuits may provide a promising platform for simulating intriguing physics of quantum many-body systems.

国内各大高校、科研机构物理学术讲座列表

---

十大热门文章

END