Topological quantum field theory (TQFT) is a very powerful theoretical tool to study topological phases and phase transitions. In 2+1D, it is well known that the Chern-Simons theory captures all the universal topological data of topological phases, e.g., quasi-particle braiding statistics, chiral central charge and even provides us a deep insight into the nature of topological phase transitions. Recently, topological phases of quantum matter are also intensively studied in 3+1D and it has been shown that loop like excitations obey the so-called three-loop-braiding statistics. In this talk, I will discuss a TQFT framework to understand the quantum statistics of loop like excitations in 3+1D. Most surprisingly, this new class of 3+1D TQFT even provides us a new route towards a quantum theory of gravity.

简介：
Prof. Zheng-Cheng Gu received his Bachelor degree in 2003 and Ph.D. degree in 2007 from Tsinghua University. From 2007 to 2009 he was a postdoctoral fellow at MIT. From 2009 to 2012 he was an associate specialist at KITP, UCSB. Since 2012 he became a director's fellow at Perimeter Institute and an adjunct professor at University of Waterloo. From 2016 to now, he is an associate professor at the Chinese University of Hong Kong. His primary research area is the theoretical study of strongly correlated quantum systems. He did a lot of work on intrinsic topological order, symmetry protected topological order, tensor networks, and lattice fractional quantum hall systems. Most of them are highly cited. He also has a board interest in high-energy physics, such as the origin of three generations of neutrinos and quantum gravity.