Towards Generalized Dimers for GTPs: $\mathcal{N}=2$ Fractional Branes at Infinite Coupling
Generalized Toric Polygons (GTPs) extend the geometric realization of $5d$ superconformal field theories beyond toric Calabi-Yau 3-folds to general $(p,q)$ 5-brane webs ending on 7-branes. We take significant steps towards the generalization of brane tilings for GTPs, or equivalently, the corresponding quiver theories. We focus on GTPs connected to ordinary toric diagrams by polytope mutations. Parallel 5-brane legs of a $(p,q)$ web define $\mathcal{N}=2$ fractional branes bounded by the corresponding parallel zig-zag paths in the brane tiling obtained by treating the GTP as an ordinary toric diagram. We propose that terminating multiple 5-branes on a common 7-brane, the defining feature of GTPs, translates into bringing these zig-zag paths together, thereby shrinking the corresponding $\mathcal{N}=2$ fractional branes to zero size in a process we call $\mathcal{N}=2$ strip condensation. We show that strip condensation follows from mirror symmetry when the coefficients in the Newton polynomial are tuned to the GTP point. We further support this proposal through several non-trivial consistency checks. In particular, it correctly reproduces the expected number of gauge groups, given equivalently by that of the mutation-related toric diagram or by the number of $T$-cones in a tessellation of the GTP. We verify this for all examples previously considered in the literature, as well as for a new infinite family of GTPs with arbitrarily large $T$-cones. Strip condensation drives the corresponding gauge groups to infinite coupling. Confinement then yields quivers that coincide with those of the mutation-related toric diagrams up to vector pairs and adjoint fields, suggesting that GTP quivers are related to those of the corresponding toric diagrams by relevant deformations, extending to GTPs the known correspondence between polytope mutations and relevant deformations.