Quantum Vortex Strings: A Review
David Tong
TL;DR
This review establishes a quantitative 2d–4d correspondence by studying non-Abelian vortex strings: their worldsheet dynamics on a $CP^{N-1}$ target space mirrors the quantum physics of the parent 4d gauge theory. In ${N}=2$ theories, the exact 4d BPS spectrum is reproduced by the 2d BPS spectrum on the string, and the Argyres-Douglas fixed points map to 2d superconformal fixed points. For ${N}=1$ theories, the heterotic ${N}=(0,2)$ string reveals dynamical SUSY breaking and restoration linked to Seiberg's quantum deformed moduli space, with intricate scale matching between the 2d and 4d theories. The work also discusses multi-string moduli spaces, domain walls, and potential extensions to dualities and non-supersymmetric contexts, highlighting a broad framework where 2d soliton dynamics encode rich information about 4d gauge theories.
Abstract
The quantum worldsheet dynamics of vortex strings contains information about the 4d non-Abelian gauge theory in which the string lives. Here I tell this story. The string worldsheet theory is typically some variant of the CP^{N-1} sigma-model, describing the orientation of the string in a U(N) gauge group. Qualitative parallels between 2d sigma-models and 4d non-Abelian gauge theories have been known since the 1970s. The vortex string provides a quantitative link between the two. In 4d theories with N=2 supersymmetry, the exact BPS spectrum of the worldsheet coincides with the bulk spectrum in 4d. Moreover, by tuning parameters, the CP^{N-1} sigma-model can be coaxed to flow to an interacting conformal fixed point which is related to the 4d Argyres-Douglas fixed point. For theories with N=1 supersymmetry, the worldsheet theory suffers dynamical supersymmetry breaking and, more interestingly, supersymmetry restoration, in a way which captures the physics of Seiberg's quantum deformed moduli space.
