title: Relative criterion for validity of a semiclassical approach to the dynamics near quantum critical points.
abstract: Based on an analysis of Feynman's path integral formulation of the propagator, a relative criterion is proposed for validity of a semiclassical approach to the dynamics near critical points in a class of systems undergoing quantum phase transitions. It is given by an effective Planck constant, in the relative sense that a smaller effective Planck constant implies better performance of the semiclassical approach. Numerical tests of this relative criterion are given in the XY model and in the Dicke model.
authors.affiliation: Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Pinquan
authors.initials: P
authors.lastname: Qin
authors.affiliation: Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China.
authors.forename: Wen-ge
authors.initials: WG
authors.lastname: Wang