The differential graded Verlinde formula and the Deligne Conjecture

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  • Christoph Schweigert
  • Lukas Woike

A modular category (Formula presented.) gives rise to a differential graded modular functor, that is, a system of projective mapping class group representations on chain complexes. This differential graded modular functor assigns to the torus the Hochschild chain complex and, in the dual description, the Hochschild cochain complex of (Formula presented.). On both complexes, the monoidal product of (Formula presented.) induces the structure of an (Formula presented.) -algebra, to which we refer as the differential graded Verlinde algebra. At the same time, the modified trace induces on the tensor ideal of projective objects in (Formula presented.) a Calabi–Yau structure so that the cyclic Deligne Conjecture endows the Hochschild cochain and chain complex of (Formula presented.) with a second (Formula presented.) -structure. Our main result is that the action of a specific element (Formula presented.) in the mapping class group of the torus transforms the differential graded Verlinde algebra into this second (Formula presented.) -structure afforded by the Deligne Conjecture. This result is established for both the Hochschild chain and the Hochschild cochain complex of (Formula presented.). In general, these two versions of the result are inequivalent. In the case of Hochschild chains, we obtain a block diagonalization of the Verlinde algebra through the action of the mapping class group element (Formula presented.). In the semisimple case, both results reduce to the Verlinde formula. In the non-semisimple case, we recover after restriction to zeroth (co)homology earlier proposals for non-semisimple generalizations of the Verlinde formula.

OriginalsprogEngelsk
TidsskriftProceedings of the London Mathematical Society
Vol/bind126
Udgave nummer6
Sider (fra-til)1811-1841
ISSN0024-6115
DOI
StatusUdgivet - 2023

Bibliografisk note

Funding Information:
We would like to thank Adrien Brochier, Lukas Müller, Cris Negron, Peter Schauenburg, and Nathalie Wahl for helpful discussions. Christoph Schweigert is supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy—EXC 2121 “Quantum Universe”—390833306. Lukas Woike gratefully acknowledges support by the Danish National Research Foundation through the Copenhagen Centre for Geometry and Topology (DNRF151) and by the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Program (Grant Agreement Number: 772960).

Publisher Copyright:
© 2023 The Authors. The publishing rights in this article are licensed to the London Mathematical Society under an exclusive licence.

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