Ensemble inequivalence and absence of quasi-stationary states in long-range random networks

Abstract

Ensemble inequivalence has been previously displayed only for long-range interacting systems with non-extensive energy. In order to perform the thermodynamic limit, such systems require an unphysical, so-called, Kac rescaling of the coupling constant. We here study models defined on long-range random networks, which avoid such a rescaling. The proposed models have an extensive energy, which is however non-additive. For such long-range random networks, pairs of sites are coupled with a probability decaying with the distance $r$ as $1/r^{\delta }$. In one dimension and with $0\le \delta <1$, surface energy scales linearly with the network size, while for $\delta >1$ it is $O(1)$. By performing numerical simulations, we show that a negative specific heat region is present in the microcanonical ensemble of a Blume-Capel model, in correspondence with a first-order phase transition in the canonical one. This proves that ensemble inequivalence is a consequence of $non$-$additivity$ rather than $non$-$extensivity$. Moreover, since a mean-field coupling is absent in such networks, relaxation to equilibrium takes place on an intensive time scale and quasi-stationary states are absent.

10 pages, 6 figures. Updated version for publication

References in corpus (9)

• Critical phenomena in complex networks
• Statistical mechanics and dynamics of solvable models with long-range interactions
• Breaking of ensemble equivalence in networks
• Diluted one-dimensional spin glasses with power law decaying interactions
• Structural properties of spatially embedded networks
• Ising model in clustered scale-free networks
• Ensemble inequivalence in random graphs
• Majority-vote model on spatially embedded networks: crossover from mean-field to Ising universality classes
• Ensemble Inequivalence in the Spherical Spin Glass Model with Nonlinear Interactions

Cited by in corpus (1)

• Complete analysis of ensemble inequivalence in the Blume-Emery-Griffiths model