The Mori Dream Space property for blow-ups of projective spaces at points and lines

Series
Algebra Seminar
Time
Tuesday, October 22, 2019 - 1:30pm for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Zhuang He – Northeastern University – he.zhu@husky.neu.eduhttps://hezhuangblog.wordpress.com/
Organizer
Bo Lin

Mori Dream Spaces are generalizations of toric varieties and, as the name suggests, Mori's minimal model program can be run for every divisor. It is known that for n5, the blow-up of Pn at r very general points is a Mori Dream Space iff rn+3. In this talk we proceed to blow up points as well as lines, by considering the blow-up X of P3 at 6 points in very general position and all the 15 lines through the 6 points. We find that the unique anticanonical section of X is a Jacobian K3 Kummer surface S of Picard number 17. We prove that there exists an infinite-order pseudo-automorphism of X, whose restriction to S is one of the 192 infinite-order automorphisms constructed by Keum.  A consequence is that there are infinitely many extremal effective divisors on X; in particular, X is not a Mori Dream Space. We show an application to the blow-up of Pn (n3) at (n+3) points and certain lines.  We relate this pseudo-automorphism to the structure of the birational automorphism group of P3. This is a joint work with Lei Yang.