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Approximating simple locally compact groups by their dense subgroups

Presented by: 
Phillip Wesolek
Thursday 11th May 2017 - 11:30 to 12:30
INI Seminar Room 1
Co-authors: Pierre-Emmanuel Caprace (Université catholique de Louvain), Colin Reid (University of Newcastle, Australia )  The collection of topologically simple totally disconnected locally compact (t.d.l.c.) groups which are compactly generated and non-discrete, denoted by , forms a rich and compelling class of locally compact groups. Members of this class include the simple algebraic groups over non-archimedean local fields, the tree almost automorphism groups, and groups acting on cube complexes.

 In this talk, we study the non-discrete t.d.l.c. groups which admit a continuous embedding with dense image into some group  ; that is, we study the non-discrete t.d.l.c. groups which approximate 
groups  . We consider a class which contains all such t.d.l.c. groups and show enjoys many of the same properties previously established for . Using these more general results, new restrictions on the members of are obtained. For any , we prove that any infinite Sylow pro- subgroup of a compact open subgroup of is not solvable. We prove further that there is a finite set of primes such that every compact subgroup of is virtually pro- .
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University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons