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SUMMARY:Chris Lazda (University of Warwick)
DTSTART:20210318T150000Z
DTEND:20210318T160000Z
DTSTAMP:20260423T021324Z
UID:ZAG/104
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/ZAG/104/">A 
 Neron-Ogg-Shafarevich criterion for K3 surfaces</a>\nby Chris Lazda (Unive
 rsity of Warwick) as part of ZAG (Zoom Algebraic Geometry) seminar\n\n\nAb
 stract\nThe naive analogue of the Néron-Ogg-Shafarevich criterion fails f
 or K3 surfaces\, that is\, there exist K3 surfaces over Henselian\, discre
 tely valued fields K\, with unramified etale cohomology groups\, but which
  do not admit good reduction over K. Assuming potential semi-stable reduct
 ion\, I will show how to correct this by proving that a K3 surface has goo
 d reduction if and only if is second cohomology is unramified\, and the as
 sociated Galois representation over the residue field coincides with the s
 econd cohomology of a certain “canonical reduction” of X. This is join
 t work with B. Chiarellotto and C. Liedtke.\n
LOCATION:https://researchseminars.org/talk/ZAG/104/
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