Bose-Fermi duality and entanglement entropies

Understand

Entanglement (Renyi) entropies of spatial regions are a useful tool for characterizing the ground states of quantum field theories.

• In this paper we investigate the extent to which these are universal quantities for a given theory, and to which they distinguish different theories, by comparing the entanglement spectra of the massless Dirac fermion and the compact free boson in two dimensions.
• We show that the calculation of Renyi entropies via the replica trick for any orbifold theory includes a sum over orbifold twists on all cycles.
• In a modular-invariant theory of fermions, this amounts to a sum over spin structures.