Projectivity of the moduli of branchvarieties

Fri Apr 11, 2025 4:00 p.m.—5:00 p.m.
Exterior of Sheffield-Sterling-Strathcona Hall featuring a stone carving of Yale's coat of arms and motto

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Seminar: 
Geometry, Symmetry and Physics

Event time: 
Friday, April 11, 2025 - 4:00pm

Location: 
KT801

Speaker: 
Andres Fernandez Herrero

Speaker affiliation: 
University of Pennsylvania

Event description: 
It is a fact of life that the moduli of (reduced) equidimensional subvarieties of projective space is often not complete. In 2010, Alexeev and Knutson introduced a compactification called the moduli of branchvarieties. This is a proper Deligne-Mumford stack parameterizing equidimensional varieties equipped with a finite morphism to projective space. In principle, this is a great parameter space to carry out GIT constructions of moduli of varieties. However, there is one main caveat to this: Alexeev and Knutson left as an open problem whether their proper DM stack is projective. In this talk, I will explain a proof of projectivity obtained in joint work with Dan Halpern-Leistner, Trevor Jones and Ritvik Ramkumar.