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SUMMARY:Undecidability in geometry and topology - Henry Wilton (University
  of Cambridge)
DTSTART:20171012T140000Z
DTEND:20171012T150000Z
UID:TALK72433@talks.cam.ac.uk
CONTACT:Dr Hansen
DESCRIPTION:There is a beautiful tension in topology between positive clas
 sification theorems and negative “no-go” theorems. The positive result
 s come from geometry\, and often derive ultimately from analysis. The nega
 tive results\, by contrast\, come from undecidability results in logic.  I
 ’ll give a survey of the history of this tension\, and mention the highl
 ight theorems — examples include Markov’s theorem that 4-manifolds can
 not be classified (on the negative side)\, and Perelman’s Geometrization
  Theorem in dimension 3 (on the positive side).   I’ll then go on to des
 cribe some recent undecidability results\, which limit possible computatio
 ns in matrix groups.  This is joint work with Martin Bridson.\n
LOCATION:MR 14\, CMS
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