Rényi entropy of locally excited states with thermal and boundary effect in 2D CFTs

Abstract: We study R\'enyi entropy of locally excited states with considering the thermal and boundary effects respectively in two dimensional conformal field theories (CFTs). Firstly we consider locally excited states obtained by acting primary operators on a thermal state in low temperature limit. The R\'enyi entropy is summation of contribution from thermal effect and local excitation. Secondly, we mainly study the R\'enyi entropy of locally excited states in 2D CFT with a boundary. We show that the evolution of R\'enyi entropy does not depend on the choice of boundary conditions and boundary will change the time evolution of R\'enyi entropy. Moreover, in 2D rational CFTs with a boundary, we show that the R\'enyi entropy always coincides with the log of quantum dimension of the primary operator during some periods of the evolution. We make use of a quasi-particle picture to understand this phenomenon. In terms of quasi-particle interpretation, the boundary behaves as an infinite potential barrier which reflects any energy moving towards the boundary.