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UID:20250927T173455EDT-2021WgwWJH@132.216.98.100
DTSTAMP:20250927T213455Z
DESCRIPTION:Title: Extension properties and separability of groups: a conne
 ction between model theory and profinite topologies\n\nAbstract: Hall's th
 eorem states that free groups have an abundance of 'separable' subsets\, i
 .e.\, sets which are closed in its profinite topology\, and so free groups
  have strong decision properties. Strengthenings of this theorem have thus
  attracted much attention in geometric group theory\, but naturally\, thes
 e results are hard to come by. Notably\, Ribes and ZalesskiÄ­ proved that p
 roducts of finitely generated subgroups of free groups are separable\, set
 tling a long-standing problem in finite monoid theory\, and later\, a brea
 kthrough by Herwig and Lascar provided a formal equivalence between this t
 heorem and extension properties of partial automorphisms of certain finite
  structures\, which are of independent interest in model theory. In this t
 alk\, I will present Coulbois' generalization of the Herwig-Lascar equival
 ence to arbitrary groups\, and also present a combinatorial proof of a gen
 eralization of the Ribes-ZalesskiÄ­ theorem to other profinite topologies\,
  due to Auinger and Steinberg\, which is also in the spirit of extending p
 artial automorphisms.\n\n \n
DTSTART:20250923T153000Z
DTEND:20250923T163000Z
LOCATION:Room 920\, Burnside Hall\, CA\, QC\, Montreal\, H3A 0B9\, 805 rue 
 Sherbrooke Ouest
SUMMARY:Zhaoshen Zhai (91Ö±²¥)
URL:/mathstat/channels/event/zhaoshen-zhai-mcgill-univ
 ersity-367917
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