Abstract:
This thesis deals with the study of quantum entanglement across spatial boundaries in
conformal-invariant quantum eld theories (2d CFT) in two dimensions. In 2d CFT, R enyi
entropy and entanglement entropy has been evaluated successfully using the replica method
for non-compact systems at zero and non-zero temperatures and for compact systems at
zero temperature (Ref.[2],[4]). However, for a compact system at nite temperature, an
exact evaluation of the entropy measure using the replica trick has not been successfully
performed. In order to gain more insights into the problem, calculations have been done by
approximating the system to a compact system at zero temperature and expanding about it
to obtain the leading order correction term to the entropy measure (Ref.[6]). In this thesis we
propose a method to calculate the second correction term and eventually a general approach
for calculating higher order correction terms to R enyi entropy and entanglement entropy at
low temperature expansion for a spatially compacti ed 1d system.
