报告人:陶勇,苏黎世联邦理工学院
时间:4月24日(周二)15:00
单位:中科院理论物理所
地点:新楼6420会议室
尽管许多生物个体的行为非常简单,但在其数量达到某个阈值时,就展现出群体的智能行为,这是生物学中一种非常有趣的现象。比如,研究蚂蚁习性的专家Nigel R. Franks就发现:单个蚂蚁可能是已知的行为最简单的生物,将100只蚂蚁放在一个平面上,它们会不断往外绕圈直到体力耗尽死去;但是,如果将上百万只蚂蚁放到一起,群体就会组成一个整体,从而形成具有集群智能的“超级生物”。人类的大脑也具有与蚂蚁群相类似的特性,单个神经元并不具有智能,但是由数百亿神经元组成的大脑却呈现高度的智能。同样道理,蚂蚁群、神经网络以及其他生物群落所表现出的集群智能行为,也应当出现在拥有更高智能等级的物种之中。我们的研究显示人类社会作为一个生物群落,也呈现出高度的集群智能行为(技术进步),而社会熵恰好是人类群体智能大小的度量。我们的研究还进一步显示,不同于物理熵,社会熵呈现出“自我指涉”的特征。Douglas Hofstadter曾在其名著《哥德尔、艾舍尔、巴赫—集异璧之大成》中将“自我指涉”联系到“自我意识”的形成,因此我们猜测人类社会的群体行为类似于一个“社会脑”。
报告人:Ulf-G. Meißner,University of Bonn / Jülich Research Center
时间:4月26日(周四)10:00,4月27日(周五)10:00,4月26日(周六)10:00
单位:中科院理论物理所
地点:ITP New Building 6620
I) Short Introduction
II) Effective Field Theories
III) Chiral QCD Dynamics
IV) Testing Chiral Dynamics in Hadron-Hadron Scattering
V) Nuclear Forces from EFT
VI) Chiral Dynamics in Nuclei
More emphasis will be put on the foundations rather than on specific calculations.
报告人:陶勇,苏黎世联邦理工学院
时间:4月25日(周三)15:00
单位:中科院理论物理所
地点:新楼6420会议室
物理系统中的玻尔兹曼分布被用于构造人工神经网络,俗称“玻尔兹曼机”,该工作导致了目前非常热的深度学习系统。我们的研究发现:人类社会作为一个生物系统,其收入分布也服从玻尔兹曼分布,但不同于物理系统的是,该生物系统的社会熵具有“自我指涉”的特征。我们将具有“自我指涉”熵的玻尔兹曼分布称为“自指玻尔兹曼分布”。在更早的工作中我们发现,由于社会熵的“自我指涉”特性,人类社会可能类似于一个“社会脑”。因此,我们尝试利用“自指玻尔兹曼分布”来构造具有“自我指涉”特性的人工神经网络,并称之为:“自指”玻尔兹曼机。相比于物理系统的玻尔兹曼机,我们期待基于生物系统的“自指”玻尔兹曼机可以改进目前的深度学习系统。
报告人:段远源,清华大学
时间:4月24日(周二)14:30
单位:中科院理化所
地点:1号楼403会议室
新能源及余热利用是缓解能源紧张形势及减轻环境污染的重要途径。有机朗肯循环(ORC)是实现中低温热能热功转换的重要手段。报告将介绍本领域的重要进展,及通过使用非共沸介质、改进循环形式等方式提升循环效率、提高热经济性方面的研究成果。
报告人:Hongbao Zhang,北京师范大学
时间:4月24日(周二)15:00
单位:中科院高能物理所
地点:Theoretical Physics Division, 319
To guarantee the predictive power of classical general relativity, Penrose proposed his cosmic censorship on the inevitable singularity formed by gravitational collapse. On the other hand, weak gravity conjecture is supposed to be one of the most important criteria for a complete theory of quantum gravity. In this talk, the speaker will talk about both of them and their very relation. In
报告人:K. Pomorski,Marie Curie-Sklodowska University
时间:4月24日(周二)15:00
单位:中科院理论物理所
地点:新楼6420会议室
The potential-energy surfaces of an extended set of heavy and super-heavy even-even nuclei with 92 ≤ Z ≤ 126 and isospin 40 ≤ N - Z ≤ 74 are evaluated within the recently developed Fourier shape parametrization. Ground-state and decay properties are studied for 324 different even-even isotopes in a four-dimensional deformation space, de fined by non-axiality, quadrupole, octupole, and hexadecapole degrees of freedom. Nuclear deformation energies are evaluated in the framework of the macroscopic-microscopic approach, with the Lublin-Strasbourg-Drop model and a Yukawa-folded mean- field potential. The evolution of the ground-state equilibrium shape and possible shape-isomeric states is studied as a function of Z and N. Alpha-decay Q-values and half-lives, as well as fission-barrier heights, are deduced. In order to understand the transition from asymmetric to symmetric fission along the Fm isotopic chain, the properties of all identified fission paths are investigated. Good agreement is found with experimental data wherever available. New interesting features about the population of different fission modes for nuclei beyond Fm are predicted.报告人:Giacomo Cacciapaglia,
时间:4月25日(周三)15:30
单位:清华大学
地点:物理系理科楼C109
Defining an underlying theory based on gauge-fermion interactions can provide essential information about the structure and properties of composite Higgs models. Firstly, non-minimal models are strongly preferred by minimal underlying theories, opening the case for a composite Dark Matter. Further, additional light states are also predicted and they may be the first sign of such models at the LHC. I will discuss exotic signatures that arise commonly in composite Higgs models. I will also briefly discuss how input from the Lattice can help guide the experimental searches.
报告人:何林, 北京师范大学
时间:4月25日(周三)16:00
单位:清华大学
地点:理科楼郑裕彤讲堂
转角作为一个全新的自由度可以调控双层石墨烯的结构和电学性质。在本报告中,我将介绍双层转角石墨烯体系中一系列角度依赖的物理性质和几种新奇量子物态。随着转角的变小,双层有转角石墨烯体系低能区的费米速度不断下降,在第一个魔角(约为1.11?)的时候费米速度降为零,体系低能量能带结构中出现平带。此时,体系中电子-电子相互作用能远大于载流子动能,从而产生强关联量子物态,例如最近在该体系发现的莫特绝缘体态和超导态。另外,在角度小于第一个魔角的双层有转角石墨烯体系中,由于堆垛结构的变化还能形成受拓扑保护的边界态网络。
9 Quantum liquids in one dimension
报告人:Xiwen Guan
时间:4月25日(周三)16:00
单位:北京大学
地点:Room W563, Physics Building
Interacting spins, bosons and fermions in one dimension (1D) provide a paradigm of many-body phenomena ranging from quantum liquid to quantum criticality. However, how can such different constituent particles form the same type of collective motion (the TLL) and how do they comprise the same universality class of quantum criticality that still lack a comprehensive understanding. In this talk, using Bethe ansatz solutions, I will discuss fundamental 1D many-body phenomena of the Tomonaga-Luttinger liquid, the Fulde-Ferrell-Larkin-Ovchinnikov Fermi liquid, quantum criticality and spin-charge separation in the Lieb-Liniger gas, the spin-1/2 Heisenberg chain and the Yang-Gaudin Fermi gas. Our results shed light on many-body phenomena of higher dimensional quantum systems.
10超高场磁共振成像——发展与技术挑战
报告人:杨文晖
时间:4月26日(周四)10:00
单位:中科院物理所
地点:M楼253
磁共振成像研究可细分为磁共振成像技术研究和磁共振成像应用研究。由于其特殊的成像物理特性,磁共振成像在临床医学和生命科学应用中获得了广泛的应用。然而,磁共振成像在方法和序列的发展上,始终超前于应用的发展,其原因主要是受制于硬件水平的进步。在几十年的发展过程中,磁共振成像的主磁场强度提高了二十多倍,达到了人体成像的7T和动物成像的21T,其成像水平也得到了显著的提升。随着生命科学研究的深入,特别是脑科学研究的发展,提出对10—100微米级空间分辨率成像的需求,人类磁共振成像也向超高场发展。磁共振成像在技术本质上就是对主磁场、梯度磁场和射频磁场的产生与调控进行研究,随着主磁场强度的提高,这三个磁场的产生和调控都面临新的挑战。如何构建稳定而均匀的9.4T—25T超高磁场是磁学技术发展面临的技术问题,对于超高磁场对应的射频磁场问题、以及超高分辨率带来的超高梯度切换率问题,都需要创新的研究。
报告人:Jianfeng Wu,Xiamen Univ
时间:4月26日(周四)14:00
单位:清华大学
地点:蒙民伟科技南楼S727
Strong and broad emission lines in the optical/UV band are a hallmark feature of type 1 quasars. However, during the past ~20 years, the Sloan Digital Sky Survey has discovered ~200 type 1 quasars with weak or no broad emission lines, the so-called "Weak Emission-Line Quasars" (WLQs). Although a small population, WLQs may provide a unique perspective to the quasar broad line region and accretion disk structure. We investigated the nature of WLQs via their X-ray properties and found that about half of the WLQs are X-ray weak by a factor of >3; the fraction is much higher than that of typical type 1 quasars (a few percent). The X-ray weak WLQs have very hard X-ray spectra, indicating substantial absorption. On the other hand, the X-ray normal WLQs have soft X-ray spectra, which is consistent with a high Eddington ratio. Based on these results, we proposed a "shielding gas" model to unify the X-ray weak and X-ray normal WLQs via orientation effect. The thick inner accretion disk caused by a high Eddington ratio may serve the role of shielding gas. I will conclude my talk by discussing the cosmological significance and future perspectives of WLQ study.
报告人:Wenbin Yan,Yau mathematical sciences center, Tsinghua University
时间:4月26日(周四)16:00
单位:清华大学
地点:理科楼郑裕彤讲堂
There is a close relationship between physics and topology. In this talk, we will start from simple examples which demonstrate the interaction of these two fields. Then we will review the basic notion of gauge theory, topological field theory and supersymmetry which are helpful in connecting topology with physics. In the end we will talk about current research in this field.
3. 太阳能电池的明天
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10. 周末大家谈—赵凯华讲述“中国物理教育从无到有并达到国际水平的历程”(下篇)
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