K-Decompositions and 3d Gauge Theories
Tudor Dimofte, Maxime Gabella, Alexander B. Goncharov
TL;DR
K-Decompositions and 3d Gauge Theories develops a comprehensive framework uniting the geometry of framed flat $PGL(K,\mathbb{C})$-connections on admissible 3-manifolds with 3d $\mathcal{N}=2$ gauge theories $T_K[M]$. The authors introduce hypersimplicial $K$-decompositions to parametrize bulk-boundary data via octahedra, construct $K_2$-Lagrangian subvarieties $\mathcal{L}_K(M)\subset \mathcal{X}^{\mathrm{un}}_K(\partial M)$, and formulate a Symplectic Gluing framework consistent with 2--3 moves. They connect these geometric constructions to a physical dictionary of cluster-like UV Lagrangians for $T_K[M]$, exhibit explicit higher-$K$ tetrahedron theories with growing combinatorial complexity, and explore knot-complement theories where $K^3$ scaling and flavor/marginal structures emerge. The paper also develops a Bloch/$K_2$-theoretic viewpoint, giving isotropy/Lagrangian statements and variation formulas for framed flat connections and motivating a large-$K$ holographic interpretation via Chern-Simons volumes. Overall, it provides a detailed, constructive path from 3-manifold triangulations to quantum field theories, their partition functions, and their large-$K$ behavior, underpinning the 3d-3d correspondence in the $K>2$ regime.
Abstract
This paper combines several new constructions in mathematics and physics. Mathematically, we study framed flat PGL(K,C)-connections on a large class of 3-manifolds M with boundary. We define a space L_K(M) of framed flat connections on the boundary of M that extend to M. Our goal is to understand an open part of L_K(M) as a Lagrangian in the symplectic space of framed flat connections on the boundary, and as a K_2-Lagrangian, meaning that the K_2-avatar of the symplectic form restricts to zero. We construct an open part of L_K(M) from data assigned to a hypersimplicial K-decomposition of an ideal triangulation of M, generalizing Thurston's gluing equations in 3d hyperbolic geometry, and combining them with the cluster coordinates for framed flat PGL(K)-connections on surfaces. Using a canonical map from the complex of configurations of decorated flags to the Bloch complex, we prove that any generic component of L_K(M) is K_2-isotropic if the boundary satisfies some topological constraints (Theorem 4.2). In some cases this implies that L_K(M) is K_2-Lagrangian. For general M, we extend a classic result of Neumann-Zagier on symplectic properties of PGL(2) gluing equations to reduce the K_2-Lagrangian property to a combinatorial claim. Physically, we use the symplectic properties of K-decompositions to construct 3d N=2 superconformal field theories T_K[M] corresponding (conjecturally) to the compactification of K M5-branes on M. This extends known constructions for K=2. Just as for K=2, the theories T_K[M] are described as IR fixed points of abelian Chern-Simons-matter theories. Changes of triangulation (2-3 moves) lead to abelian mirror symmetries that are all generated by the elementary duality between N_f=1 SQED and the XYZ model. In the large K limit, we find evidence that the degrees of freedom of T_K[M] grow cubically in K.
