5月18日物理论坛报告《Wandering amongst the Feynman Diagrams》 [2012-05-16]

报告题目：Wandering amongst the Feynman Diagrams

报告人：Prof. Nikolay Prokofiev (Univ. of Massachusetts, Amherst)

报告地点：物理学院二楼学术报告厅

报告时间：5月18日周五下午4:00

报告摘要:
Feynman diagrams are the most celebrated and powerful tool of theoretical physics. Nearly all key models in  natural science are subject to the Feynman’s diagrammatic technique. However, in the strongly correlated regime, i.e. no small parameters, it is often considered useless/hopeless and is reduced to just one(!) lowest-order self-consistent diagram. I will argue that diagrammatic expansions form a suitable basis for numerical simulations of interacting many-body systems with enormous and yet to be explored potential. The first application of the new technique which performs stochastic summation of millions of fully dressed irreducible Feynman diagrams and extrapolates results to the infinite diagram order was to the unitary gas of ultra-cold fermions. This strongly correlated system is of interest to condensed-matter, statistical, and high-energy physics because of its fundamental connections to high-Tc superconductivity, neutron matter, rich phase diagram, and polaron physics. Excellent agreement with highly accurate thermodynamic data from MIT for 6Li atoms everywhere in the normal phase establishes Bold Diagrammatic Monte Carlo as a reliable unbiased method for dealing with strongly correlated quantum matter. Among other advantages one may mention that results are obtained for thermodynamic (and finite) systems at any temperature, lattice, continuous, short-range, and long-range models can be dealt with by the same approach.

报告人简介:
Nikolay Prokofiev，美国麻省大学Amherst分校教授。最近十余年主要从事凝聚态系统中的临界现象与新奇物质态的研究。在1998年，与Svistunov教授一起发明了计算物理中著名的蠕虫算法。特别是两人以此为基础，进一步提出了基于费曼图的蒙特卡洛算法，该算法使计算高阶费曼图成为可能，一定程度上突破了强耦合极限，并成功解决了一批强关联费米子系统的相关问题。Nikolay在超固体的理论解释、�壁超流性、解禁闭量子相变理论以及基于玻色子、费米子的超冷原子量子模拟等方面均有诸多贡献。