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SUMMARY:Exposé de Simon Rigby (Gand): Cohomological invariants and trace
forms of algebras with involution
DTSTART;VALUE=DATE-TIME:20211125T130000Z
DTEND;VALUE=DATE-TIME:20211125T140000Z
DTSTAMP;VALUE=DATE-TIME:20211208T011038Z
UID:indico-event-7057@indico.math.cnrs.fr
DESCRIPTION:Many cohomological invariants of algebraic groups are related
to trace forms of algebras\, including all the invariants of PGL4\, G2\, a
nd F4 in mod 2 Galois cohomology. In the talk\, I will discuss some exampl
es of nonassociative (structurable) algebras with involution that play a r
ole in constructing groups of type E6\, E7\, and E8\, and show how to extr
act cohomological invariants from their trace forms. The hope is for thes
e invariants to survive the constructions and produce invariants of except
ional algebraic groups. I will present some partial progress in that direc
tion\, as well as a surprising discovery of a degree 5 cohomological invar
iant of PGSp8 (or symplectic involutions of degree 8). This is based on j
oint work with Victor Petrov.\n\nhttps://indico.math.cnrs.fr/event/7057/
LOCATION:Saint-Etienne (Métare) C112
URL:https://indico.math.cnrs.fr/event/7057/
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