The statistical mechanics and machine learning of the $\alpha$-Rényi ensemble

Abstract

We study the statistical physics of the classical Ising model in the so-called $\alpha$-Rényi ensemble, a finite-temperature thermal state approximation that minimizes a modified free energy based on the $\alpha$-Rényi entropy. We begin by characterizing its critical behavior in mean-field theory in different regimes of the Rényi index $\alpha$. Next, we re-introduce correlations and consider the model in one and two dimensions, presenting analytical arguments for the former and devising a Monte Carlo approach to the study of the latter. Remarkably, we find that while mean-field predicts a continuous phase transition below a threshold index value of $\alpha \sim 1.303$ and a first-order transition above it, the Monte Carlo results in two dimensions point to a continuous transition at all $\alpha$. We conclude by performing a variational minimization of the $\alpha$-Rényi free energy using a recurrent neural network (RNN) ansatz where we find that the RNN performs well in two dimensions when compared to the Monte Carlo simulations. Our work highlights the potential opportunities and limitations associated with the use of the $\alpha$-Rényi ensemble formalism in probing the thermodynamic equilibrium properties of classical and quantum systems.

18 pages, 11 figures

References in corpus (8)

• Computational complexity and fundamental limitations to fermionic quantum Monte Carlo simulations
• Discovering Phases, Phase Transitions and Crossovers through Unsupervised Machine Learning: A critical examination
• Minimally Entangled Typical Thermal State Algorithms
• Efficient tensor network simulation of IBM's Eagle kicked Ising experiment
• Efficient tensor network simulation of IBM's largest quantum processors
• Data-Enhanced Variational Monte Carlo Simulations for Rydberg Atom Arrays
• Neural network approach to quasiparticle dispersions in doped antiferromagnets
• Enhancing variational Monte Carlo using a programmable quantum simulator