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UID:20251126T025219EST-0660KDF1nb@132.216.98.100
DTSTAMP:20251126T075219Z
DESCRIPTION:Title: Crystallographic Helly groups.\n\nAbstract: A Helly grap
 h is a graph in which the metric balls form a Helly family: any pairwise i
 ntersecting collection of balls has nonempty total intersection. A Helly g
 roup is a group that acts properly and cocompactly on a Helly graph. Helly
  groups simultaneously generalize hyperbolic\, cocompactly cubulated and C
 (4)-T(4) graphical small cancellation groups while maintaining nice proper
 ties\, such as biautomaticity. I will show that if a crystallographic grou
 p is Helly then its point group preserves an L^{infinity} metric on R^n. T
 hus we will obtain some new nonexamples of Helly groups\, including the 3-
 3-3 Coxeter group\, which is a systolic group. This answers a question pos
 ed by Chepoi during the recent Simons Semester on Geometric and Analytic G
 roup Theory in Warsaw.\n
DTSTART:20191030T190000Z
DTEND:20191030T200000Z
LOCATION:Room 1104\, Burnside Hall\, CA\, QC\, Montreal\, H3A 0B9\, 805 rue
  Sherbrooke Ouest
SUMMARY:Nima Hoda\, École normale supérieure
URL:/mathstat/channels/event/nima-hoda-ecole-normale-s
 uperieure-302027
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