Quasi BPS Wilson loops, localization of loop equation by homology and exact beta function in the large N limit of SU(N) Yang-Mills theory

TL;DR

This paper introduces a novel localization method for large-N Yang-Mills theory using homological techniques, leading to an exact beta function and insights into non-commutative ASD vortices, with potential implications for understanding quark confinement.

Contribution

It develops a homological localization approach for the loop equation in large-N YM theory, deriving an exact beta function and connecting to non-commutative ASD vortices.

Findings

Localization on special quasi BPS Wilson loops avoids divergences.

Beta function is saturated by non-commutative ASD vortices.

Derived an NSVZ-type exact beta function matching perturbative coefficients.

Abstract

We localize the loop equation of large-N YM theory in the ASD variables on a critical equation for an effective action by means of homological methods as opposed to the cohomological localization of equivariantly closed forms in local field theory. Our localization occurs for some special simple quasi BPS Wilson loops, that have no perimeter divergence and no cusp anomaly for backtracking cusps, in a partial Eguchi-Kawai reduction from four to two dimensions of the non-commutative theory in the limit of infinite non-commutativity and in a lattice regularization in which the ASD integration variables live at the points of the lattice, thus implying an embedding of parabolic Higgs bundles in the YM functional integral. We find that the beta function of the effective action is saturated by the non-commutative ASD vortices of the EK reduction. An exact canonical beta function of NSVZ type that reproduces the universal first and second perturbative coefficients follows by the localization on vortices. Finally we argue that a scheme can be found in which the canonical coupling coincides with the physical charge between static quark sources in the large-N limit and we compare our theoretical calculation with some numerical lattice result.