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CATEGORIES:Applied and Computational Analysis
SUMMARY:Undecidability in geometry and topology - Henry Wi
 lton (University of Cambridge)
DTSTART;TZID=Europe/London:20171012T150000
DTEND;TZID=Europe/London:20171012T160000
UID:TALK72433AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/72433
DESCRIPTION:There is a beautiful tension in topology between p
 ositive classification theorems and negative “no-g
 o” theorems. The positive results come from geomet
 ry\, and often derive ultimately from analysis. Th
 e negative results\, by contrast\, come from undec
 idability results in logic.  I’ll give a survey of
  the history of this tension\, and mention the hig
 hlight theorems — examples include Markov’s theore
 m that 4-manifolds cannot be classified (on the ne
 gative side)\, and Perelman’s Geometrization Theor
 em in dimension 3 (on the positive side).   I’ll t
 hen go on to describe some recent undecidability r
 esults\, which limit possible computations in matr
 ix groups.  This is joint work with Martin Bridson
 .\n
LOCATION:MR 14\, CMS
CONTACT:Dr Hansen
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