Ferromagnetic and spin-glass like transition in the $q$-neighbor Ising model on random graphs

TL;DR

This paper explores a nonequilibrium $q$-neighbor Ising model on random graphs, revealing complex phase transitions including ferromagnetic and spin-glass-like states, with results supported by Monte Carlo simulations and analytical approximations.

Contribution

It introduces a detailed analysis of phase transitions in a $q$-neighbor Ising model with mixed interactions, extending mean-field and pair approximations to account for antiferromagnetic effects.

Findings

Phase diagrams show first- and second-order ferromagnetic transitions.

Identification of spin-glass-like phases at certain parameters.

Quantitative agreement between simulations and analytical predictions near critical points.

Abstract

The $q$-neighbor Ising model is investigated on homogeneous random graphs with a fraction of edges associated randomly with antiferromagnetic exchange integrals and the remaining edges with ferromagnetic ones. It is a nonequilibrium model for the opinion formation in which the agents, represented by two-state spins, change their opinions according to a Metropolis-like algorithm taking into account interactions with only a randomly chosen subset of their $q$ neighbors. Depending on the model parameters in Monte Carlo simulations phase diagrams are observed with first-order ferromagmetic transition, both first- and second-order ferromagnetic transitions and second-order ferromagnetic and spin-glass-like transitions as the temperature and fraction of antiferromagnetic exchange integrals are varied; in the latter case the obtained phase diagrams qualitatively resemble those for the dilute spin-glass model. Homogeneous mean-field and pair approximations are extented to take into account the effect of the antiferromagnetic exchange interactions on the ferromagnetic phase transition in the model. For a broad range of parameters critical temperatures for the first- or second-order ferromagnetic transition predicted by the homogeneous pair approximation show quantitative agreement with those obtained from Monte Carlo simulations; significant differences occur mainly in the vicinity of the tricritical point in which the critical lines for the second-order ferromagnetic and spin-glass-like transitions meet.