Classical isomorphism theorems due to Dynkin, Eisenbaum, Le Jan, and Sznitman
establish equalities between the correlation functions or distributions of occupation
times of random paths or ensembles of paths and Markovian fields, such as the
discrete Gaussian free field. We extend these results to the case of real, complex, or
quaternionic vector bundles of arbitrary rank over graphs endowed with a connection,
by providing distributional identities between functionals of the Gaussian free vector
field and holonomies of random paths. As an application, we give a formula for
computing moments of a large class of random, in general non-Gaussian,
fields in terms of holonomies of random paths with respect to an annealed
random gauge field, in the spirit of Symanzik’s foundational work on the
subject.
Keywords
discrete potential theory, Laplacian on vector bundles,
Gaussian free vector field, random walks, covariant
Feynman–Kac formula, Poissonian ensembles of Markovian
loops, local times, isomorphism theorems, discrete gauge
theory, holonomy