Physical review. B, Condensed matter
Exact expressions for diagonal correlation functions in the d=2 Ising model
Ranjan K. Ghosh, Robert E. Shrock
Abstract
We present exact explicit expressions for the diagonal spin-spin correlation functions $〈{\ensuremath{\sigma}}_{00}{\ensuremath{\sigma}}_{\mathrm{nn}}〉$ in the $d=2$ Ising model, in terms of elliptic integrals, for $n$ up to 6. We also give a general structural formula for $〈{\ensuremath{\sigma}}_{00}{\ensuremath{\sigma}}_{\mathrm{nn}}〉$ and discuss its properties.