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SUMMARY:Peter Feller (ETH  Zurich)
DTSTART:20211015T150000Z
DTEND:20211015T161500Z
DTSTAMP:20260423T005659Z
UID:CIRGET/45
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/CIRGET/45/">
 Braids\, quasimorphisms\, and slice-Bennequin inequalities</a>\nby Peter F
 eller (ETH  Zurich) as part of CRM - Séminaire du CIRGET / Géométrie et
  Topologie\n\n\nAbstract\nThe writhe of a braid (=#pos crossing - #neg cro
 ssings) and the fractional Dehn twist coefficient of a braid (a rational n
 umber that measures "how much the braid twists") are the two most prominen
 t examples of what is known as a quasimorphism (a map that fails to be a g
 roup homomorphism by at most a bounded amount) from Artin's braid group on
  n-strands to the reals. We consider characterizing properties for such qu
 asimorphisms and talk about relations to the study of knot concordance. Fo
 r the latter\, we consider inequalities for quasimorphisms modelled after 
 the so-called slice-Bennequin inequality: writhe(B) <= 2g_4(K) - 1 + n for
  all n-stranded braids B with closure a knot K. Based on work in progress.
 \n
LOCATION:https://researchseminars.org/talk/CIRGET/45/
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