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SUMMARY:Xinyu Fang (Harvard)
DTSTART:20260219T220000Z
DTEND:20260219T233000Z
DTSTAMP:20260422T220134Z
UID:STAGE/149
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/STAGE/149/">
 Descent obstruction and the local-global principle for torsors</a>\nby Xin
 yu Fang (Harvard) as part of STAGE\n\nLecture held in Room 2-139 in the MI
 T Simons Building.\n\nAbstract\nWe start with a quick overview of the desc
 ent obstruction for the Hasse principle\, indicating how torsors and $H^1(
 k\,G)$ show up in this context. \nNext\, we introduce contracted products 
 and twisted torsors\, which will be important for us later. Finally\, we d
 iscuss finiteness results for torsors over local fields and the local-glob
 al principle for torsors. These will be useful when we discuss unramified 
 torsors and the descent obstruction in more detail later.\n\nReference: \n
 \n1) Poonen\, <a href="https://math.mit.edu/~poonen/papers/Qpoints.pdf"><i
 >Rational points on varieties</i></a>\, Sections 8.4.7\, 5.12.5-5.12.8\, a
 nd 6.5.6.\n\n2) Skorobogatov\, Torsors and rational points\, Section 2.2.\
 n
LOCATION:https://researchseminars.org/talk/STAGE/149/
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