Anisotropy and universality: the Oslo model, the rice pile experiment and the quenched Edwards-Wilkinson equation

TL;DR

This paper demonstrates that anisotropy shifts the Oslo model to a different universality class, providing exact exponents and linking it to the quenched Edwards-Wilkinson equation with drift, with implications for experimental observations.

Contribution

It establishes the impact of anisotropy on universality classes and offers an exact solution connecting the Oslo model to the quenched Edwards-Wilkinson equation with drift.

Findings

Anisotropy changes the universality class of the Oslo model.

Exact exponents for the anisotropic model are derived.

Anisotropy may explain experimental inconsistencies in rice pile studies.

Abstract

We show that any amount of anisotropy moves the Oslo model to another known universality class, the exponents of which can be derived exactly. This amounts to an exact solution of the quenched Edwards-Wilkinson equation with a drift term. We argue that anisotropy is likely to be experimentally relevant and may explain why consistent exponents have not been extracted in the rice pile experiments.