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University Park
Altoona

Tuesday, February 17, 2009
4:00 pm, 256 Hawthorn

Patrick Brosnan
The University of British Columbia

Essential dimension and algebraic stacks.

Abstract: Essential dimension is measure of the number of parameters needed to define an algebraic object. It is a notion which was ``in the air'' in one form or another for many years (depending on your viewpoint). For example, the ancients knew how to reduce the number of parameters needed to define a quadratic field extension to 1.
However, the rigorous definition was given relatively recently by J. Buhler and Z. Reichstein. I will discuss joint work with Reichstein and A. Vistoli on the essential dimension of algebraic stacks and its application to the number of parameters needed to define a quadratic form with a Spin structure.

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We meet weekly on Friday afternoons at Penn State Altoona (and sometimes at Penn State University Park). If you are interested in giving a talk in our seminar please contact one of the coordinators for the Spring 2009 semester: Wojtek Dorabiala and Aissa Wade.

 

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