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Extensions of Grothendieck's theorem on principal bundles over the projective line

Presented by: 
M Thaddeus [Columbia]
Tuesday 21st June 2011 - 11:30 to 12:30
INI Seminar Room 2
Let G be a split reductive group over a field. Grothendieck and Harder proved that any principal G-bundle over the projective line reduces (essentially uniquely) to a maximal torus. In joint work with Johan Martens, we show that this remains true when the base is a chain of lines, a football, a chain of footballs, a finite abelian gerbe over any of these, or the stack-theoretic quotient of any of these by a torus action.
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University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons