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SUMMARY:Chris Lazda (Warwick)
DTSTART:20200715T090000Z
DTEND:20200715T100000Z
DTSTAMP:20260423T005750Z
UID:notts_ag/15
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/notts_ag/15/
 ">A Neron-Ogg-Shafarevich criterion for $K3$ surfaces</a>\nby Chris Lazda 
 (Warwick) as part of Online Nottingham algebraic geometry seminar\n\n\nAbs
 tract\nThe naive analogue of the Néron-Ogg-Shafarevich criterion fails fo
 r $K3$ surfaces\, that is\, there exist $K3$ surfaces over Henselian\, dis
 cretely valued fields $\\mathbb{K}$\, with unramified étale cohomology gr
 oups\, but which do not admit good reduction over $\\mathbb{K}$. Assuming 
 potential semi-stable reduction\, I will show how to correct this by provi
 ng that a $K3$ surface has good reduction if and only if is second cohomol
 ogy is unramified\, and the associated Galois representation over the resi
 due field coincides with the second cohomology of a certain "canonical red
 uction" of $X$. This is joint work with B. Chiarellotto and C. Liedtke.\n
LOCATION:https://researchseminars.org/talk/notts_ag/15/
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