Fisher-Hartwig expansion for the transverse correlation function in the XX spin-1/2 chain

Motivated by the recent results on the asymptotic behavior of Toeplitz determinants with Fisher-Hartwig singularities, we develop an asymptotic expansion for transverse spin correlations in the XX spin-1/2 chain. The coefficients of the expansion can be calculated to any given order using the relation to discrete Painleve equations. We present explicit results up to eleventh order and compare them with a numerical example.