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SUMMARY:Chris Kottke (New College of Florida)
DTSTART:20210226T160000Z
DTEND:20210226T171500Z
DTSTAMP:20260423T005702Z
UID:CIRGET/34
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/CIRGET/34/">
 Bigerbes and applications</a>\nby Chris Kottke (New College of Florida) as
  part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstra
 ct\nGerbes are geometric objects on a space which represent degree 3 integ
 er cohomology\, in the same way that complex line bundles (classified by t
 he Chern class) represent cohomology in degree 2. Among other settings\, t
 hey arise naturally as obstructions to lifting the structure group of a pr
 incipal G-bundle to a U(1) central extension of G. \nHigher versions of ge
 rbes\, representing cohomology classes of degree 4 and up\, are typically 
 complicated by higher categorical concepts (2-morphisms and so on) in thei
 r definition. In contrast\, bigerbes (and their higher cousins) admit a si
 mple\, geometric\, non-higher-categorical description\, and provide a sati
 sfactory account of the relationship between so-called `string structures'
  on a manifold and `fusion spin structures' on its loop space\, among othe
 r applications. This is based on recent joint work with Richard Melrose.\n
LOCATION:https://researchseminars.org/talk/CIRGET/34/
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