Consortium Distinguished Lecture Series
Grigory Mikhalkin

Ellipsoid Superpotentials:
Obstructing Symplectic Embeddings by Singular Algebraic Curves

Professor Grigory Mikhalkin
University of Geneva

Wednesday, March 20, 2024, 4:00pm (Sofia Time)
ICMS - Sofia, Hall 403

Abstract: How singular can be a local branch of a plane algebraic curve of a given degree d? A remarkable series of real algebraic curves was constructed by Stepan Orevkov. It is based on even-indexed numbers in the Fibonacci series: a degree 5 curve with a 13/2 cusp, a degree 13 curve with a 34/5-cusp, and so on. We discuss this and other series of algebraic curves in the context of the problem of symplectic packing of an ellipsoid into a ball, with the answer given by the spectacular Fibonacci staircase of McDuff and Schlenk. The aspect ratio a>1 of the ellipsoid can be viewed as a real parameter for a certain enumerative superpotential function, which is mostly locally constant, but jumps at certain specific rational values (responsible for the aspects of cusp singularities). Based on joint work with Kyler Siegel.