Relations on $\overline{\mathcal{M}}_{g,n}$ and the negative $r$-spin Witten conjecture

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Main Authors: Chidambaram, Nitin Kumar, Garcia-Failde, Elba, Giacchetto, Alessandro
Format: Preprint
Published: 2022
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author Chidambaram, Nitin Kumar
Garcia-Failde, Elba
Giacchetto, Alessandro
author_facet Chidambaram, Nitin Kumar
Garcia-Failde, Elba
Giacchetto, Alessandro
contents We construct and study various properties of a negative spin version of the Witten $ r $-spin class. By taking the top Chern class of a certain vector bundle on the moduli space of twisted spin curves that parametrises $ r $-th roots of the anticanonical bundle, we construct a non-semisimple cohomological field theory (CohFT) that we call the Theta class $ Θ^r $. This CohFT does not have a flat unit and its associated Dubrovin--Frobenius manifold is nowhere semisimple. Despite this, we construct a semisimple deformation of the Theta class, and using the Teleman reconstruction theorem, we obtain tautological relations on $ \overline{\mathcal{M}}_{g,n} $. We further consider the descendant potential of the Theta class and prove that it is the unique solution to a set of $ \mathcal{W} $-algebra constraints, which implies a recursive formula for the descendant integrals. Using this result for $ r = 2 $, we prove Norbury's conjecture which states that the descendant potential of $ Θ^2 $ coincides with the Brézin--Gross--Witten tau function of the KdV hierarchy. Furthermore, we conjecture that the descendant potential of $ Θ^r $ is the $ r $-BGW tau function of the $ r $-KdV hierarchy and prove the conjecture for $ r = 3 $.
format Preprint
id arxiv_https___arxiv_org_abs_2205_15621
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Relations on $\overline{\mathcal{M}}_{g,n}$ and the negative $r$-spin Witten conjecture
Chidambaram, Nitin Kumar
Garcia-Failde, Elba
Giacchetto, Alessandro
Algebraic Geometry
Mathematical Physics
14H10, 14H70 (Primary) 37K20, 81R12 (Secondary)
We construct and study various properties of a negative spin version of the Witten $ r $-spin class. By taking the top Chern class of a certain vector bundle on the moduli space of twisted spin curves that parametrises $ r $-th roots of the anticanonical bundle, we construct a non-semisimple cohomological field theory (CohFT) that we call the Theta class $ Θ^r $. This CohFT does not have a flat unit and its associated Dubrovin--Frobenius manifold is nowhere semisimple. Despite this, we construct a semisimple deformation of the Theta class, and using the Teleman reconstruction theorem, we obtain tautological relations on $ \overline{\mathcal{M}}_{g,n} $. We further consider the descendant potential of the Theta class and prove that it is the unique solution to a set of $ \mathcal{W} $-algebra constraints, which implies a recursive formula for the descendant integrals. Using this result for $ r = 2 $, we prove Norbury's conjecture which states that the descendant potential of $ Θ^2 $ coincides with the Brézin--Gross--Witten tau function of the KdV hierarchy. Furthermore, we conjecture that the descendant potential of $ Θ^r $ is the $ r $-BGW tau function of the $ r $-KdV hierarchy and prove the conjecture for $ r = 3 $.
title Relations on $\overline{\mathcal{M}}_{g,n}$ and the negative $r$-spin Witten conjecture
topic Algebraic Geometry
Mathematical Physics
14H10, 14H70 (Primary) 37K20, 81R12 (Secondary)
url https://arxiv.org/abs/2205.15621