Single Interval R\'enyi Entropy At Low Temperature

Abstract

In this paper, we calculate the R\'enyi entropy of one single interval on a circle at finite temperature in 2D CFT. In the low temperature limit, we expand the thermal density matrix level by level in the vacuum Verma module, and calculate the first few leading terms in $e^{-\pi/TL}$ explicitly. On the other hand, we compute the same R\'enyi entropy holographically. After considering the dependence of the R\'enyi entropy on the temperature, we manage to fix the interval-independent constant terms in the classical part of holographic R\'enyi entropy. We furthermore extend the analysis in Xi Dong's paper to higher orders and find exact agreement between the results from field theory and bulk computations in the large central charge limit. Our work provides another piece of evidence to support holographic computation of R\'enyi entropy in AdS$_3$/CFT$_2$ correspondence, even with thermal effect.