Non-monotonic behavior of the Binder Parameter in the discrete spin systems

TL;DR

This paper investigates the non-monotonic behavior of the Binder parameter in discrete spin systems, revealing its origin and proposing new order parameters to mitigate this issue, especially in Potts models with q=3 and 4.

Contribution

The study identifies the origin of non-monotonic Binder parameter behavior and introduces new order parameters to reduce or eliminate this effect in discrete spin systems.

Findings

Binder parameters are non-monotonic for q=3 and 4 in Potts models.

The non-monotonicity originates from the low-temperature term in the improved estimator.

New order parameters can reduce or eliminate the non-monotonic behavior.

Abstract

We study a non-monotonic behavior of the Binder parameter, which appears in the discrete spin systems. We show that the Binder parameters of the Potts model are non-monotonic for $q=3$ and $4$, while they are monotonic for the Ising case ($q=2$). Using the Fortuin-Kasteleyn graph representation, we find that the improved estimator of the Binder parameter consists of two terms with values only in high- and low-temperature regions. The non-monotonic behavior is found to originate from the low-temperature term. With the appropriately defined order parameter, we can reduce the influence of the low-temperature term, and as a result, the non-monotonic behavior can also be reduced. We propose new definitions of the order parameter, which reduces or eliminates the non-monotonic behavior of the Binder parameter in a system for which the improved estimator of the Binder parameter is unknown.