Negative fluctuation-dissipation ratios in the backgammon model

TL;DR

This paper investigates fluctuation-dissipation relations in the Backgammon model, revealing a negative fluctuation-dissipation ratio that diverges over time, indicating possible negative effective temperatures in glassy systems without thermal activation.

Contribution

It demonstrates the existence of a universal negative fluctuation-dissipation ratio in the Backgammon model at zero temperature, independent of the observable.

Findings

Negative fluctuation-dissipation ratio observed

Ratio diverges linearly with waiting time

Negative effective temperature possible without thermal activation

Abstract

We analyze fluctuation-dissipation relations in the Backgammon model: a system that displays glassy behavior at zero temperature due to the existence of entropy barriers. We study local and global fluctuation relations for the different observables in the model. For the case of a global perturbation we find a unique negative fluctuation-dissipation ratio that is independent of the observable and which diverges linearly with the waiting time. This result suggests that a negative effective temperature can be observed in glassy systems even in the absence of thermally activated processes.