BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:The boundary of hyperbolic free-by-cyclic groups - Yael Algom Kfir
  (University of Haifa)
DTSTART:20170621T090000Z
DTEND:20170621T100000Z
UID:TALK73015@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:Given an automorphism $\\phi$ of the free group $F_n$ consider
  the HNN extension $G = F_n \\rtimes_\\phi \\Z$.&nbsp\;We compare two case
 s:<br>1. $\\phi$ is induced by a pseudo-Anosov map on a &nbsp\;surface wit
 h boundary and of non-positive Euler characteristic. In this case $G$ is a
  CAT(0) group with isolated flats and its (unique by Hruska) CAT(0)-bounda
 ry is a Sierpinski Carpet (Ruane).<br>2. $\\phi$ is atoroidal and fully ir
 reducible. Then by a theorem of Brinkmann $G$ is hyperbolic. If $\\phi$ is
  irreducible then Its boundary&nbsp\;is homeomorphic to the Menger curve (
 M. Kapovich and Kleiner).&nbsp\;<br>We prove that if $\\phi$ is atoroidal 
 then its boundary contains a non-planar set. Our proof highlights the diff
 erences between the two cases above.&nbsp\;<br>This is joint work with A. 
 Hilion and E. Stark.
LOCATION:Seminar Room 1\, Newton Institute
END:VEVENT
END:VCALENDAR