- 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.edu – https://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 n≥5, the blow-up of Pn at r very general points is a Mori Dream Space iff r≤n+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 (n≥3) 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.