Pattern Expansion of Spin Glasses

TL;DR

This paper presents a systematic pattern expansion method for spin-glass Hamiltonians, revealing fundamental differences between EA and SK models and uncovering low-energy excitations.

Contribution

It introduces a novel pattern expansion technique that distinguishes EA and SK models and identifies ultra-low energy excitations in EA systems.

Findings

EA models break into isolated subconnected sections after expansion

SK model exhibits self-similar behavior with residual systems maintaining mean-field structure

Pattern expansion reveals ultra-low energy excitations with rapidly decreasing energies

Abstract

We introduce a systematic method for expanding general spin-glass Hamiltonians in terms of Mattis interactions, providing a novel perspective for understanding the fundamental differences between short-range Edwards-Anderson (EA) and mean-field Sherrington-Kirkpatrick (SK) spin glasses. By iteratively extracting patterns from the coupling matrix, we expand the original spin-glass system into a Hopfield-like model (a series of Mattis interactions) plus a residual system. Our analysis reveals profound distinctions between EA and SK models: while EA models in two and three dimensions break into isolated subconnected sections after expansion, the SK model exhibits remarkable self-similar behavior, with the residual system preserving the mean-field structure and Gaussian statistics throughout the expansion process. This self-similarity manifests in exponential decay of residual matrix norms and expansion coefficients, reflecting the inherent mean-field nature of the SK model. Furthermore, we demonstrate that pattern expansion can identify ultra-low energy excitations in EA models, revealing excitations with energies that decrease rapidly with expansion step. Through connected component analysis, we quantify the size-energy relationship of these independent excitation clusters, opening new avenues for understanding the low-energy landscape of spin glasses and providing insights into the nature of metastable states.