Dimensional reduction and its breakdown in the 3-dimensional long-range random field Ising model

TL;DR

This paper explores the conditions under which dimensional reduction holds or breaks down in a 3D long-range random field Ising model, revealing a critical point dependent on decay exponents of interactions and disorder.

Contribution

It introduces a nonperturbative functional renormalization group approach combined with supersymmetry to identify a critical value separating dimensional reduction from its breakdown.

Findings

Existence of a critical value for decay exponents where dimensional reduction breaks down.

The transition depends on specific relations between interaction and disorder decay exponents.

The results are relevant for future simulations and experimental observations.

Abstract

We investigate dimensional reduction, the property that the critical behavior of a system in the presence of quenched disorder in dimension d is the same as that of its pure counterpart in d-2, and its breakdown in the case of the random-field Ising model in which both the interactions and the correlations of the disorder are long-ranged, i.e. power-law decaying. To some extent the power-law exponents play the role of spatial dimension in a short-range model, which allows us to probe the theoretically predicted existence of a nontrivial critical value separating a region where dimensional reduction holds from one where it is broken, while still considering the physical dimension d=3. By extending our recently developed approach based on a nonperturbative functional renormalization group combined with a supersymmetric formalism, we find that such a critical value indeed exists, provided one chooses a specific relation between the decay exponents of the interactions and of the disorder correlations. This transition from dimensional reduction to its breakdown should therefore be observable in simulations and numerical analyses, if not experimentally.