The Two-Color Ext Soergel Calculus
Abstract
We compute Ext groups between Soergel Bimodules associated to the infinite/finite dihedral group for a realization in characteristic 0 and show that they are free right modules. In particular, we obtain an explicit diagrammatic basis for the Hochschild cohomology of indecomposable Soergel Bimodules. We then give a diagrammatic presentation for the corresponding monoidal category of Ext-enhanced Soergel Bimodules. As applications, we explicitly compute HOMFLY homology/triply graded link homology for the connect sum of two Hopf links and the negative torus link as right modules. Furthermore, we show that the Hochschild cohomology of Soergel Bimodules in finite dihedral type categorifies Gomi's trace, providing a analog of Soergel's Hom Formula in the dihedral setting.
Cite
@article{arxiv.2211.07802,
title = {The Two-Color Ext Soergel Calculus},
author = {Cailan Li},
journal= {arXiv preprint arXiv:2211.07802},
year = {2025}
}
Comments
Updated with new computations of HOMFLY homology and fixed typos