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DTSTART:20250309T070000
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DTSTART:20251102T060000
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DTSTART;TZID=America/Toronto:20260206T153000
SEQUENCE:0
TRANSP:TRANSPARENT
DTEND;TZID=America/Toronto:20260206T163000
URL:https://uwaterloo.ca/pure-mathematics/events/geometry-and-topology-semi
 nar-45
SUMMARY:Geometry and Topology Seminar
CLASS:PUBLIC
DESCRIPTION:DUNCAN MCCOY\, UNIVERSITÉ DU QUÉBEC À MONTRÉAL\n\n_The unk
 notting number of positive alternating knots_\n\nThe unknotting number is 
 simultaneously one of the simplest classical\nknot invariants to define an
 d one of the most challenging to compute.\nThis intractability stems from 
 the fact that typically one has no idea\nwhich diagrams admit a collection
  of crossing changes realizing the\nunknotting number for a given knot. Fo
 r positive alternating knots\,\none can show that if the unknotting number
  equals the lower bound\ncoming from the classical knot signature\, then t
 he unknotting number\ncan be calculated from an alternating diagram. I wil
 l explain this\nresult along with some of the main tools in the proof\, wh
 ich are\nprimarily from smooth 4-dimensional topology. This is joint work 
 with\nPaolo Aceto and JungHwan Park.\n\nMC 5417
DTSTAMP:20260502T043550Z
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