Algebraic and Arithmetic Geometry Seminar

Boundary divisors in the stable pair compactification of the moduli space of Horikawa surfaces

by Luca Schaffler (Roma 3)

Aula Magna (Dipartimento di Matematica)

Aula Magna

Dipartimento di Matematica

Smooth minimal surfaces of general type with $K^2=1$, $p_g=2$, and $q=0$ constitute a fundamental example in the geography of algebraic surfaces, and the 28-dimensional moduli space $M$ of their canonical models admits a geometric and modular compactification $\overline{M}$ by stable surfaces. Franciosi-Pardini-Rollenske classified the Gorenstein stable degenerations parametrized by it, and jointly with Rana they determined boundary divisors parametrizing irreducible stable surfaces with a unique T-singularity. In this talk, we continue with the investigation of the boundary of $\overline{M}$ constructing eight new irreducible boundary divisors parametrizing reducible surfaces. Additionally, we study the relation with the GIT compactification of $M$ and the Hodge theory of the degenerate surfaces that the eight divisors parametrize. This is joint work in progress with Patricio Gallardo, Gregory Pearlstein, and Zheng Zhang.