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 ξ, T - Tc and h.
Journal of Physics A Mathematical General
- Pub Date:
- September 2002
- High Energy Physics - Theory;
- Condensed Matter
- 11 pages, Latex, 3 figures. Accepted for publication in Journal of Physics A