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UID:9143@i2m.univ-amu.fr
DTSTART;TZID=Europe/Paris:20261126T110000
DTEND;TZID=Europe/Paris:20261126T120000
DTSTAMP:20260921T064644Z
URL:https://www.i2m.univ-amu.fr/evenements/shreyasharma/
SUMMARY:Shreya Sharma (Université de Bâle): Amitsur groups of G-varieties
DESCRIPTION:Shreya Sharma: Suppose a group acts on a variety. If it preserv
 es a line bundle on the variety\, must the action also lift compatibly to 
 the fibers of that line bundle? The answer is not always: there can be a c
 ohomological obstruction. The obstructions arising from all invariant line
  bundles form the Amitsur group of the action. Remarkably\, this group is 
 unchanged under equivariant\nbirational maps\, and therefore\, it can be u
 sed to distinguish group actions birationally and to obtain obstructions t
 o equivariant versions of rationality and stable rationality. After introd
 ucing the invariant through concrete examples\, I will discuss its classif
 ication in higher dimensions\, focusing on toric varieties and smooth Fano
  threefolds.
CATEGORIES:Séminaire,Géométrie et Topologie de Marseille
LOCATION:I2M Saint-Charles - Salle de séminaire\, Université Aix-Marseill
 e\, Campus Saint-Charles\, 3 Place Victor Hugo\, Marseille\, 13003\, Franc
 e
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=Université Aix-Marseille\,
  Campus Saint-Charles\, 3 Place Victor Hugo\, Marseille\, 13003\, France;X
 -APPLE-RADIUS=100;X-TITLE=I2M Saint-Charles - Salle de séminaire:geo:0,0
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TZID:Europe/Paris
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DTSTART:20261025T020000
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