Statistical physics of principal minors: Cavity approach

TL;DR

This paper develops a cavity approach to analyze the statistical physics of principal minors in matrices, estimating their partition function and entropy, with applications to quantum systems and learning data subsets.

Contribution

It introduces a Gaussian representation method within the Bethe approximation to study principal minors of positive matrices, providing asymptotic results for certain graph structures.

Findings

No phase transition observed in the studied matrix class.

Exact characterization of minors in a mean-field model.

Asymptotic accuracy for diagonally dominant matrices with tree-like structures.

Abstract

Determinants are useful to represent the state of an interacting system of (effectively) repulsive and independent elements, like fermions in a quantum system and training samples in a learning problem. A computationally challenging problem is to compute the sum of powers of principal minors of a matrix which is relevant to the study of critical behaviors in quantum fermionic systems and finding a subset of maximally informative training data for a learning algorithm. Specifically, principal minors of positive square matrices can be considered as statistical weights of a random point process on the set of the matrix indices. The probability of each subset of the indices is in general proportional to a positive power of the determinant of the associated sub-matrix. We use Gaussian representation of the determinants for symmetric and positive matrices to estimate the partition function (or free energy) and the entropy of principal minors within the Bethe approximation. The results are expected to be asymptotically exact for diagonally dominant matrices with locally tree-like structures. We consider the Laplacian matrix of random regular graphs of degree $K=2,3,4$ and exactly characterize the structure of the relevant minors in a mean-field model of such matrices. No (finite-temperature) phase transition is observed in this class of diagonally dominant matrices by increasing the positive power of the principal minors, which here plays the role of an inverse temperature.