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SUMMARY:Geordie Williamson (Sydney Mathematical Research Institute)
DTSTART:20210916T210000Z
DTEND:20210916T220000Z
DTSTAMP:20260423T021343Z
UID:ZAG/147
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/ZAG/147/">Ge
 ometric extensions</a>\nby Geordie Williamson (Sydney Mathematical Researc
 h Institute) as part of ZAG (Zoom Algebraic Geometry) seminar\n\n\nAbstrac
 t\nThe Decomposition Theorem is probably my favourite theorem. I'll start 
 by recalling the statement and trying to explain a little of why it is so 
 remarkable. One consequence is that one could imagine an alternate history
  of the subject\, in which intersection cohomology complexes were discover
 ed without knowing about perverse sheaves. I'll explain how this might hav
 e occurred\, and how it led Soergel and Juteau-Mautner-Williamson to the s
 tudy of parity sheaves. Parity sheaves need strong parity vanishing assump
 tions\, which somewhat restrict their utility (particularly for applicatio
 ns outside of geometric representation theory). The final goal of my talk 
 is to explain a recent theorem (joint with Chris Hone) which proves the ex
 istence and uniqueness of "geometric extensions" in broad generality. The 
 upshot is that parity sheaves probably don't need parity after all.\n
LOCATION:https://researchseminars.org/talk/ZAG/147/
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