Higher correlations, universal distributions and finite size scaling in the field theory of depinning

TL;DR

This paper advances the field theory of depinning by calculating higher correlation functions, revealing simplified diagrammatic rules, and analyzing universal distributions and stability properties near the critical dimension.

Contribution

It introduces a renormalizable field theory for depinning, computes higher correlation functions, and analyzes universal distributions and stability, providing new insights into the critical behavior.

Findings

Universal scaled width-distribution matches Gaussian predictions at lowest order.

Deviations from Gaussian are small and involve higher correlation functions.

Correction-to-scaling exponent is found to be -epsilon, not -epsilon/3.

Abstract

Recently we constructed a renormalizable field theory up to two loops for the quasi-static depinning of elastic manifolds in a disordered environment. Here we explore further properties of the theory. We show how higher correlation functions of the displacement field can be computed. Drastic simplifications occur, unveiling much simpler diagrammatic rules than anticipated. This is applied to the universal scaled width-distribution. The expansion in d=4-epsilon predicts that the scaled distribution coincides to the lowest orders with the one for a Gaussian theory with propagator G(q)=1/q^(d+2 \zeta), zeta being the roughness exponent. The deviations from this Gaussian result are small and involve higher correlation functions, which are computed here for different boundary conditions. Other universal quantities are defined and evaluated: We perform a general analysis of the stability of the fixed point. We find that the correction-to-scaling exponent is omega=-epsilon and not -epsilon/3 as used in the analysis of some simulations. A more detailed study of the upper critical dimension is given, where the roughness of interfaces grows as a power of a logarithm instead of a pure power.