We propose a new class of universal amplitude ratios which involve the first terms of the short distance expansion of the correlators of a statistical model in the vicinity of a critical point. We will describe the critical system with a conformal field theory (UV fixed point) perturbed by an appropriate relevant operator. In two dimensions the exact knowledge of the UV fixed point allows for a...

We have extended our method of grouping of Feynman diagrams (GFD theory) to study the transversal and longitudinal Greens functions G ⊥ (k) and G (k) in ϕ 4 model below the critical point (T < T c) in presence of an infinitesimal external field. Our method allows a qualitative analysis not cutting the perturbation series. We have shown that the critical behavior of the Greens functions is consi...

A new perturbation theory is proposed for studying finite-size effects near critical point of the φ 4 model with a one-component order parameter. The new approach is based on the techniques of generating functional and functional derivative with respect to external source field and can be used for temperatures both above and below the critical point of the bulk system. It is shown that this app...

We study an eigenvalue problem by a non-smooth critical point theory. Under general assumptions, we prove the existence of at least one solution as a minimum of a constrained energy functional. We apply some results on critical point theory with symmetry to provide a multiplicity result.

Keywords: Dirichlet boundary value problem p-Laplacian Topological degree theory Critical point theory Weak solution a b s t r a c t In this work, by virtue of topological degree theory and critical point theory, we are mainly concerned with the existence of weak solutions for a Dirichlet boundary value problem with the p-Laplacian operator.