$\mathrm{U}(N)$ lattice Yang-Mills in the 't Hooft regime
Ron Nissim
TL;DR
This work establishes a mass gap, a unique infinite-volume limit, and a large-$N$ limit for $\,\mathrm{U}(N)\,$ lattice Yang–Mills in the 't Hooft regime by overcoming the failure of the Bakry–Émery approach for $\,\mathrm{U}(N)\$ through a random-environment decomposition into $\,\mathrm{U}(1)\times\mathrm{SU}(N)\$. It combines cluster expansions with Langevin-dynamics arguments to prove a mass gap and decorrelation bounds, and uses a marginal SU(N) analysis to derive a mass gap for the marginal field, enabling a robust infinite-volume limit. The Large-$N$ analysis then shows Wilson loops become deterministic and factorize in probability, extending the Wilson-loop factorization property to $\,\mathrm{U}(N)\$. The results provide a rigorous foundation for the strong-coupling, 't Hooft scaling regime of $\ ext{U}(N)$ lattice YM and highlight a productive synthesis of cluster expansions and stochastic dynamics in non-Abelian gauge theories. Overall, the paper broadens the scope of rigorous lattice YM results to include $ ext{U}(N)$ and strengthens connections to large-$N$ and string-theoretic viewpoints.
Abstract
We establish a mass gap, prove the existence of a unique infinite volume limit, and give a new proof of the large $N$ limit for $\mathrm{U}(N)$ lattice Yang-Mills theory in the 't Hooft regime. These results were previously obtained for $\mathrm{SU}(N)$ and $\mathrm{SO}(N)$ lattice Yang-Mills theories as applications of the mixing of the associated Langevin dynamics, which is verified via the Bakry-Émery criterion [SZZ23]. For $\mathrm{U}(N)$, however, this approach fails because its Ricci curvature is not uniformly positive, and as a result the Bakry-Émery condition cannot be easily verified. To overcome this obstacle, we recast the $\mathrm{U}(N)$ theory as a random-environment $\mathrm{SU}(N)$ model, where the randomness arises from a $\mathrm{U}(1)$ field, and combine cluster-expansion and Langevin-dynamics techniques to analyze the resulting $\mathrm{U}(1)\times\mathrm{SU}(N)$ model.
