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Math-Physics Joint Seminar

Tuesday, October 10, 2023 - 5:15pm

Andres Fernandez Herrero

Penn, Columbia, MPI


University of Pennsylvania


Andres will give another talk at AGNES over the weekend.

For any given complex projective curve C and reductive group G, Simpson's Non Abelian Hodge Theorem (NAHT) establishes a diffeomorphism between: 
(1) the de Rham moduli space of semistable G-bundles with a flat connection on C, and
(2) the Dolbeault moduli space of semistable Higgs G-bundles on C.
If we replace the complex numbers with a field of positive characteristic, then the Dolbeault and de Rham moduli spaces share a lot of similarities from the point of view of algebraic geometry. For example, both admit nontrivial proper fibrations onto affine spaces via the Hitchin fibration and the p-curvature morphism. In fact, there is a strong version of the NAHT in positive characteristic due to Chen and Zhu, which establishes an algebraic isomorphism between:
(1) the stack of flat G-connections on C, and
(2) a twisted form of the stack of Higgs G-bundles on the Frobenius twist C'.
The Chen-Zhu isomorphism does not preserve semistability, so the NAHT in positive characteristic does not directly descend to the level of moduli spaces. In this talk, I will explain how to construct a version of the NAHT in positive characteristic that preserves semistability, hence inducing an algebraic identification of the de Rham moduli space with a twisted form of the Dolbeault moduli space. As a consequence, we obtain an isomorphism between the intersection cohomologies of both moduli spaces, and identify the decomposition theorems for the Hitchin fibration and the p-curvature morphism.
This talk is based on joint work in progress with Siqing Zhang.