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SUMMARY:Alexei Skorobogatov (Imperial)
DTSTART:20211203T100000Z
DTEND:20211203T110000Z
DTSTAMP:20260404T111409Z
UID:HannoverNTAGS/1
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/Hanno
 verNTAGS/1/">Enriques quotients of K3 surfaces and associated Brauer class
 es</a>\nby Alexei Skorobogatov (Imperial) as part of Hannover Number Theor
 y and Arithmetic Geometry Seminar\n\n\nAbstract\nThis is a joint work in p
 rogress with Domenico Valloni. Let X be a complex K3 surface with an Enriq
 ues quotient S. It is known that the Brauer group of S has a unique non-ze
 ro element. Beauville gave a criterion for the natural map from Br(S) to B
 r(X) to be injective. Extending a result of Keum\, who proved that every K
 ummer surface has an Enriques quotient\, we show for an arbitrary Kummer s
 urface X that every element of Br(X) of order 2 comes from an Enriques quo
 tient of X. Work of Ohashi implies that in some `generic' cases this gives
  a bijection between the set of elements of order 2 in Br(X) and the set o
 f Enriques quotients of X.\n
LOCATION:https://stable.researchseminars.org/talk/HannoverNTAGS/1/
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SUMMARY:Teppei Takamatsu (Kyoto University)
DTSTART:20230414T084500Z
DTEND:20230414T094500Z
DTSTAMP:20260404T111409Z
UID:HannoverNTAGS/2
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/Hanno
 verNTAGS/2/">On Quasi-Frobenius-splitting</a>\nby Teppei Takamatsu (Kyoto 
 University) as part of Hannover Number Theory and Arithmetic Geometry Semi
 nar\n\n\nAbstract\nIn algebraic geometry of positive characteristics\, sin
 gularities defined by the Frobenius map\, including the notion of Frobeniu
 s-splitting\, have played a crucial role.\nYobuko introduced the notion of
  quasi-Frobenius-splitting and Frobenius-split heights\, which generalize 
 and quantify the notion of F-splitting\, and proved that Frobenius-split h
 eights coincide with Artin-Mazur heights for Calabi-Yau varieties.\nIn thi
 s talk\, I want to explain recent results obtained on quasi-Frobenius-spli
 tting (specifically\, some criteria and properties).\nThis talk is based o
 n joint work with Tatsuro Kawakami\, Hiromu Tanaka\, Jakub Witaszek\, Fuet
 aro Yobuko\, and Shou Yoshikawa.\n
LOCATION:https://stable.researchseminars.org/talk/HannoverNTAGS/2/
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