Long-distance asymptotics of spin–spin correlation functions for the XXZ spin chain Original Research Article

We study asymptotic expansions of spin–spin correlation functions for the XXZ Heisenberg chain in the critical regime. We use the fact that the long-distance effects can be described by the Gaussian conformal field theory. Comparing exact results for form factors in the XYZ and sine-Gordon models, we determine correlation amplitudes for the leading and main subleading terms in the asymptotic expansions of spin–spin correlation functions. We also study the isotropic (XXX) limit of these expansions.