Classification of 4d N=2 gauge theories
Lakshya Bhardwaj, Yuji Tachikawa
TL;DR
The paper delivers a complete framework to classify four-dimensional $N{=}2$ UV-complete gauge theories built from semisimple gauge groups and hypermultiplets by encoding theories as associated graphs of nodes (gauge factors) and polygons (hypermultiplets). It shows that UV-complete theories fall into three categories, and that the graph is restricted to either a single loop or a trunk with branches, leading to a finite set of allowed trunks and decorations. The authors explicitly enumerate possible nodes, $1$-gons, $2$-gons, and the rare $3$-gons, reduce non-conformal theories to conformal seeds via mass deformations, and provide a detailed two-part classification covering all semisimple cases. They summarize the status of Seiberg-Witten solutions across the resulting theories, highlighting where curves are known (via Donagi-Witten, class S, or instanton counting) and where open cases remain, and they offer an explicit algorithm and Mathematica implementation to generate the full catalog. The work provides a comprehensive map of traditional $N{=}2$ UV-complete gauge theories, serving as a foundation for future SW analyses and deeper structural insights into duality and class S connections.
Abstract
We classify all possible four-dimensional N=2 supersymmetric UV-complete gauge theories composed of semi-simple gauge groups and hypermultiplets. We also give appropriate references for all theories with known Seiberg-Witten solutions.
