Towards a Direct Method for the Analyticity of the Pressure for Certain Classical Unbounded Spin Systems

Assane Lo

Published 2006-11-01, updated 2007-03-24Version 7

The aim of this paper is to study direct methods for the analyticity of the pressure for certain classical unbounded spin models. We provide a representation in terms of the Witten Laplacian on one-forms of the nth-derivative of the pressure as function of some order parameter t . The technique involves the formula for the covariance of two functions introduced by B. Helffer and J. Sjostrand.