GENERAL
SEMINAR

“Finite
separating sets and quasi-affine quotients”

by

EMILIE
DUFRESNE

University
of Basel

Abstract:  Nagata's famous
counterexample to Hilbert's fourteenth problem shows that the ring of
invariants of an algebraic group action on an affine algebraic variety is not
always finitely generated. In some sense, however, invariant rings are not far
from being affine. Indeed, invariant rings are always quasi-affine, and finite
separating sets always exist. We give a new method for finding a quasi-affine
variety on which the ring of regular functions is equal to a given invariant
ring, and give a criterion to recognize separating algebras. We use the method
and criterion to construct new examples.

Date : June  8, 2011 (Wednesday)

Time : 15.40-16.30

Place: Bilkent University ,Mathematics Seminar Room SA141

Tea and cookies will be served before the seminar.