Line defects and (framed) BPS quivers

TL;DR

This paper develops algebraic and geometric methods using BPS quivers and laminations to analyze line defects and their framed BPS spectra in N=2 supersymmetric theories, providing algorithms and examples.

Contribution

It introduces a novel framework combining BPS quivers, laminations, and cluster algebras to compute and understand line defects and framed BPS states.

Findings

Framed BPS spectra can be computed using algebraic elements from the Leavitt path algebra.

A mutation-based algorithm derives spectra of new defects from known ones.

The formalism is illustrated with several explicit examples.

Abstract

The BPS spectrum of certain N=2 supersymmetric field theories can be determined algebraically by studying the representation theory of BPS quivers. We introduce methods based on BPS quivers to study line defects. The presence of a line defect opens up a new BPS sector: framed BPS states can be bound to the defect. The defect can be geometrically described in terms of laminations on a curve. To a lamination we associate certain elements of the Leavitt path algebra of the BPS quiver and use them to compute the framed BPS spectrum. We also provide an alternative characterization of line defects by introducing framed BPS quivers. Using the theory of (quantum) cluster algebras, we derive an algorithm to compute the framed BPS spectra of new defects from known ones. Line defects are generated from a framed BPS quiver by applying certain sequences of mutation operations. Framed BPS quivers also behave nicely under a set of "cut and join" rules, which can be used to study how N=2 systems with defects couple to produce more complicated ones. We illustrate our formalism with several examples.