Improved harmonic approximation and the 2D Ising model at T\neqT_c and h\neq 0

A. IUCCI; C. NAÓN

JOURNAL OF PHYSICS. A - MATHEMATICAL AND GENERAL

IOP

Año: 2002 vol. 35 p. 8005 - 8012

0305-4470

We propose a new method to determine the unknown parameter associated with a self-consistent harmonic approximation. We check the validity of our technique in the context of the sine-Gordon model. As a non trivial application we consider the scaling regime of the 2D Ising model away from the critical point and in the presence of a magnetic field $h$. We derive an expression that relates the approximate correlation length $\xi$, $T-T_c$ and $h$.