Eur. Phys. J. B (2014) 87: 138
https://doi.org/10.1140/epjb/e2014-50191-4

Regular Article

Extensive limit of a non-extensive entanglement entropy

Weill Cornell Medical College in Qatar, Education City, P.O. Box 24144, Doha, Qatar

^a e-mail: nik2011@qatar-med.cornell.edu

Received: 20 March 2014
Published online: 18 June 2014

Abstract

An important calculation has been that of the (von Neumann) entanglement entropy of the ground state of 1-dimensional lattice models at criticality and of their massive perturbations. This entropy turned out to be, generally, non-extensive. It was noticed, by contrast, that the Tsallis entropy of such systems can be extensive for a particular value of the non-extensive parameter. This value was expressed as function of the central charge of the underlying conformal field theory. We provide an answer to the question on why for central charge approaching infinity, extensivity of the von Neumann entropy of the ground state is restored.