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SUMMARY:Yunqing Tang (Paris-Saclay)
DTSTART:20200603T150000Z
DTEND:20200603T160000Z
DTSTAMP:20260418T063705Z
UID:LNTS/7
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LNTS/7/">Pic
 ard ranks of reductions of K3 surfaces over global fields</a>\nby Yunqing 
 Tang (Paris-Saclay) as part of London number theory seminar\n\n\nAbstract\
 nFor a K3 surface $X$ over a number field with potentially good reduction 
 everywhere\, we prove that there are infinitely many primes modulo which t
 he reduction of $X$ has larger geometric Picard rank than that of the gene
 ric fiber $X$. A similar statement still holds true for ordinary K3 surfac
 es with potentially good reduction everywhere over global function fields.
  In this talk\, I will present the proofs via the (arithmetic) intersectio
 n theory on good integral models (and its special fibers) of $\\mathrm{GSp
 in}$ Shimura varieties. These results are generalizations of the work of C
 harles on exceptional isogenies between reductions of a pair of elliptic c
 urves. This talk is based on joint work with Ananth Shankar\, Arul Shankar
 \, and Salim Tayou and with Davesh Maulik and Ananth Shankar.\n
LOCATION:https://researchseminars.org/talk/LNTS/7/
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