Action of the Cremona group on a noncommutative ring
Authors:
Alexandr Usnich
Affiliation:
University of Zurich, Institut fuer Mathematik, 190 Winterthurerstrasse, Zurich, Switzerland
Abstract:
The Cremona group acts on the field of two independent commutative variables over complex numbers. We provide a noncommutative algebra that is an analog of a noncommutative field of two independent variables and prove that the Cremona group embeds in a group of outer automorphisms of this algebra. We give two proofs of it, the first proof is technical, the second one is conceptual and proceeds through a construction of a birational invariant of an algebraic variety from its bounded derived category of coherent sheaves.