2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/126211The 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.Mathematical Physics82B05;82B26;35J15text