Geometry Seminar
April 26, Aula Dal Passo: 11:30-12:30 and 14:30-15:30
This talk is part of the activity of the MIUR Excellence Department
Project MATH@TOV CUP E83C18000100006.
Speakers
Roberto Svaldi (EPFL) & Calum Spicer (King's College London)
Title
Minimal model program for foliated surfaces: a different approach.
Abstract
The birational classification of foliated surface
is pretty much complete, thanks to the work of Brunella, Mendes,
McQuillan. In recent joint work we explore a new approach to studying
the singularities and the minimal model program for foliated surfaces
inspired by the work of Pereira-Svaldi.
The basic idea is rather simple: rather than just considering the the
canonical divisor KF of a foliation F (the
classic analogue of the canonical divisor in the foliated world)
together with the linear system |mKF|, with m positive integer,
one can consider perturbed divisors KF+εKX,
ε>0$ and linear systems of the form |nKX + mKF|,
n,m>0. Those perturbed divisors (and the related linear systems)
encode a lot of the positivity features that classically the canonical
divisor (and pluricanonical forms) on a projective variety display and
that do not necessarily hold for KF alone. The price to
pay for working with these divisors is to define a new category of
singularities for foliated varieties.
We will introduce these new singularities and try to explain how they
behave via examples in the 1st talk. The 2nd talk will instead be
devoted to discussing new results and applications for this class of
divisors, discussing new results on the boundedness of surface
foliations, and applications of these results to some classical
problems in foliation theory, for instance, on the problem of bounding
the degree of orbits of vector fields in the complex plane.