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SUMMARY:Richard Thomas (Imperial College London)
DTSTART:20200925T190000Z
DTEND:20200925T200000Z
DTSTAMP:20260407T214747Z
UID:agstanford/24
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/agstanford/2
 4/">Square root Euler classes and counting sheaves on Calabi-Yau 4-folds</
 a>\nby Richard Thomas (Imperial College London) as part of Stanford algebr
 aic geometry seminar\n\n\nAbstract\nI will explain a nice characteristic c
 lass of $SO(2n\,\\mathbf{C})$ bundles in both Chow cohomology and K-theory
 \, and how to localise it to the zeros of an isotropic section. This build
 s on work of Edidin-Graham\, Polishchuk-Vaintrob\, Anderson and many other
 s.\n\nThis can be used to construct an algebraic virtual cycle (and virtua
 l structure sheaf) on moduli spaces of stable sheaves on Calabi-Yau 4-fold
 s.\nIt recovers the real derived differential geometry virtual cycle of Bo
 risov-Joyce but has nicer properties\, like a torus localisation formula. 
 Joint work with Jeongseok Oh (KIAS).\n\nThe discussion for Richard Thomas
 ’s talk is taking place not in zoom-chat\, but at https://tinyurl.com/20
 20-09-25-rt  (and will be deleted after 3-7 days).\n
LOCATION:https://researchseminars.org/talk/agstanford/24/
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