Combinatorial correlation functions in three-dimensional eight-vertex models
Igor G. Korepanov
TL;DR
The paper develops an explicit ${\mathbb F}_2$-linear i-to-${\it t}$ spin transform for a 3D combinatorial eight-vertex model, enabling exact calculation of spin correlations on $2^n\times2^n\times2^n$ blocks under cyclic boundaries. By constructing new thick-space bases and a tensor-product transform, it reduces multi-spin probabilities to tractable Fourier-analytic expressions governed by the eigenstructure of a $3\times3$ matrix $A$ over ${\mathbb F}_2$ (and its transpose). For a concrete $A$, the authors compute single-, pair-, triple-, and quadruple-spin probabilities, revealing mostly independence for small spins but revealing nontrivial 4-spin correlations in structured configurations. The approach generalizes to multiple $A$ choices, preserving key correlation structures, and opens a pathway to rigorous analysis of 3D combinatorial spin systems without integrability assumptions. The results illustrate how algebraic self-similarity and Fourier methods yield exact, scalable insights into complex 3D spin correlation phenomena in a purely combinatorial setting.
Abstract
A new version of the self-similarity spin transform on three-dimensional cubic lattices is proposed that makes possible calculation of nontrivial spin correlations in a "combinatorial" model, in which all permitted spin configurations have equal probabilities.
