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SUMMARY:Rank gradient and cost of groups - Nikolay Nikolov (Imperial Colle
 ge London)
DTSTART:20101026T150000Z
DTEND:20101026T160000Z
UID:TALK26474@talks.cam.ac.uk
CONTACT:Pablo Candela
DESCRIPTION:I will present results from a joint paper with Miklós Abért\
 , where we study the growth of the ranks of subgroups of finite index in a
  residually finite group G\, by relating it to the notion of cost of measu
 rable group actions.\n\nMotivated by the fixed price conjecture we ask whe
 ther the speed of the growth (called rank gradient) is independent of the 
 choice of a chain of normal subgroups of G. This question is especially in
 teresting for Kleinian groups where it connects with open problems in hype
 rbolic 3-manifolds and congruence kernels of arithmetic groups.
LOCATION:MR4\, CMS
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