The Fisher-Hartwig Formula and Entanglement Entropy

Ku Vit

metric fisher and entropy entanglement

Alexander Rudol'fovich Its, V. E. Korepin

Toeplitz matrices have applications to different problems of statistical mechanics. Recently they were used for calculation of entanglement entropy in spin chains. We use the Fisher-Hartwig formula to calculate entanglement entropy of large block of spins in the ground state of XY spin chain. We also calculate Renyi entropy and prove that the spectrum of the density matrix of a block of spins is exact geometric sequence [also different eigenvalues are degenerated differently].

Dominik Janzing

Durrani, Ijaz

Bai-Qi Jin, V. E. Korepin

Fisher-Hartwig formula has been successful applied to describe the von Neumann and Rényi entropies of a block of spins in the ground state of XX spin chain. It was based on a determinant representation. In this paper, we generalize the free fermion method to obtain an exact formulation for the entropy of any finite subsystem in XX spin chain. Based on this, we derive a determinant representation of the entropy of multiple disjoint intervals in the ground state of $XX$ model.

Alexander G Abanov, Dmitri A. Ivanov, Yachao Qian

We revisit the problem of finding the probability distribution of a fermionic number of one-dimensional spinless free fermions on a segment of a given length.The generating function for this probability distribution can be expressed as a determinant of a Toeplitz matrix.We use the recently proven generalized Fisher-Hartwig conjecture on the asymptotic behavior of such determinants to find the generating function for the full counting statistics of fermions on a line segment.Unlike the method of bosonization, the Fisher-Hartwig formula correctly takes into account the discreteness of charge.Furthermore, we numerically check the precision of the generalized Fisher-Hartwig formula, find that it has a higher precision than rigorously proven so far and conjecture the form of the next-order correction to the existing formula.