Semiclassical framed BPS states

TL;DR

This paper develops a semiclassical framework for understanding framed BPS states in 4D N=2 super Yang-Mills theories with 't Hooft defects, linking geometric operators on monopole moduli space to physical BPS spectra and wall crossing phenomena.

Contribution

It introduces a semiclassical description of framed BPS states via Dirac operators on monopole moduli space and proposes a map connecting Higgs vevs to Seiberg-Witten coordinates, incorporating quantum corrections.

Findings

Established a conjectural map between Higgs vevs and Seiberg-Witten coordinates.

Linked BPS state counting to the L^2 kernel of Dirac operators on monopole moduli space.

Predicted wall crossing behavior and kernel jumps of Dirac operators in specific examples.

Abstract

We provide a semiclassical description of framed BPS states in four-dimensional N = 2 super Yang-Mills theories probed by 't Hooft defects, in terms of a supersymmetric quantum mechanics on the moduli space of singular monopoles. Framed BPS states, like their ordinary counterparts in the theory without defects, are associated with the L^2 kernel of certain Dirac operators on moduli space, or equivalently with the L^2 cohomology of related Dolbeault operators. The Dirac/Dolbeault operators depend on two Cartan-valued Higgs vevs. We conjecture a map between these vevs and the Seiberg-Witten special coordinates, consistent with a one-loop analysis and checked in examples. The map incorporates all perturbative and nonperturbative corrections that are relevant for the semiclassical construction of BPS states, over a suitably defined weak coupling regime of the Coulomb branch. We use this map to translate wall crossing formulae and the no-exotics theorem to statements about the Dirac/Dolbeault operators. The no-exotics theorem, concerning the absence of nontrivial SU(2)_R representations in the BPS spectrum, implies that the kernel of the Dirac operator is chiral, and further translates into a statement that all L^2 cohomology of the Dolbeault operator is concentrated in the middle degree. Wall crossing formulae lead to detailed predictions for where the Dirac operators fail to be Fredholm and how their kernels jump. We explore these predictions in nontrivial examples. This paper explains the background and arguments behind the results announced in a short accompanying note.