Non Perturbative Renormalization Group Approach To Some Out Of Equilibrium Systems PDF Download

Many of the most important open problems in statistical mechanics are related with systems out of thermal equilibrium. In this work we use field theory methods to study some of these systems. To do so, we first introduce a field theory representation for the systems of interest, as well as the specific formalism to be used throughout, the so-called non perturbative renormalization group (NPRG). This formalism has emerged in the last years as a very efficient way to deal with strongly correlated systems, and has been applied with success to problems both in and out of equilibrium. Before treating the actual systems of interest, we develop some new tools and methods within the NPRG context, and test them in a simple scalar field theory, belonging to the Ising universality class. We are able to obtain results for the momentum-dependent scaling function of the d=3 Ising model, without having to fix any free parameter. Also, in order to tackle in an efficient way the physics of out of equilibrium systems, we study in detail some formal aspects of their passage to a field theory representation, as well as the equivalences between different possible ways to perform this passage. After these preliminaries, we concentrate in out of equilibrium active-to-absorbing phase transitions in reaction-diffusion systems, and in particular in the subclass known as branching and annihilating random walks (BARW). Among other results, we use the NPRG to find an exact solution to any vertex in a simple system, known as pure annihilation. With this, we analyze some properties of BARW at low branching rates, by means of an expansion in the branching rate around pure annihilation. This perturbative expansion, which is performed around a nontrivial model, allows us to find some striking exact results for some of the most important universality classes in these systems.