Permutation glass

TL;DR

Permutation glasses are a new disordered system model where the energy landscape is based on permutations, revealing conditions for ordered states, absence of replica symmetry breaking, and a connection to fermion gases.

Contribution

This paper introduces permutation glasses as a novel disordered model, analyzing their phase behavior and showing they lack replica symmetry breaking.

Findings

Permutation glasses transition to ordered states below a certain temperature.

The probability of energetically favored incorrect components must be low for order to be accessible.

No permutation glass phase with replica symmetry breaking exists; residual entropy persists at zero temperature.

Abstract

The field of disordered systems provides many simple models in which the competing influences of thermal and non-thermal disorder lead to new phases and non-trivial thermal behavior of order parameters. In this paper, we add a model to the subject by considering a system where the state space consists of various orderings of a list. As in spin glasses, the disorder of such "permutation glasses" arises from a parameter in the Hamiltonian being drawn from a distribution of possible values, thus allowing nominally "incorrect orderings" to have lower energies than "correct orderings" in the space of permutations. We analyze a Gaussian, uniform, and symmetric Bernoulli distribution of energy costs, and, by employing Jensen's inequality, derive a general condition requiring the permutation glass to always transition to the correctly ordered state at a temperature lower than that of the non-disordered system, provided that this correctly ordered state is accessible. We in turn find that in order for the correctly ordered state to be accessible, the probability that an incorrectly-ordered component is energetically favored must be less than the inverse of the number of components in the system. We show that all of these results are consistent with a replica symmetric ansatz of the system and argue that there is no permutation glass phase characterized by replica symmetry breaking, but there is glassy behavior represented by a residual entropy at zero temperature. We conclude by discussing an apparent duality between permutation glasses and fermion gases.