Speaker: John Lesieutre
Affiliation: Pennsylvania State University, USA
Title of Talk: Cremona homomorphisms from Severi varieties
Date: April 08, 2026
Time: 16:00:00 Hours
Venue: Ramanujan Guesthouse, 1st floor conference room

Abstract: Let Cr(n) denote the n-dimensional Cremona group, the group of birational self-maps of P^n. Gizatullin constructed a homomorphism Cr(2) -> Cr(5), defined using generators and relations for Cr(2). I will give a more geometric interpretation of this map, and then explain several generalizations of this map to higher-dimensional settings based on the geometry of the four Severi varieties, which are related to the four finite-dimensional real division algebras. I'll describe some applications to questions about degree growth of rational maps, as well as some higher-dimensional interpolation questions.