Andrea di Lorenzo: Degenerations of twisted maps to algebraic stacks

Date: 2023-05-30

Time: 09:45 - 10:45

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Andrea di Lorenzo, Humboldt-Universität zu Berlin


Given a family of smooth curves over a punctured disk, in order to extend this family to a family over (a ramified cover of) the whole disk, we have to allow the central fiber to be a stable nodal curve. If we want to extend families of curves together with some “additional data” (e.g. a vector bundle over the family, a fibration in elliptic curves over the family, G-torsors, etc), then the problem becomes more complicated, and in general stable nodal curves might not be enough (think of the case of curves plus line bundles, or admissible covers).  In this talk I will present a result that says that, if we allow the central fiber to be a nodal twisted curve whose coarse space is quasi stable (i.e. it might contain rational components with two marked points), then we can always extend the original family of curves plus “additional data” (e.g. vector bundle, fibration, G-torsor,…) to a family over the whole disk, as long as the “additional data” is given by maps to quotient stacks admitting a projective good moduli space. Moreover, the algorithm for extending this family is quite explicit.

This is joint work with Giovanni Inchiostro.