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DTSTAMP:20250805T192306Z
DESCRIPTION:Title: Train tracks\, orbigraphs\, and CAT(0) free-by-cyclic gr
 oups.\n\n \n\nAbstract: Given φ:Fn→Fnφ:Fn→Fn an automorphism of a free gro
 up of rank nn\, there is an associated free-by-cyclic group Fn⋊φZFn⋊φZ\, w
 hich may be thought of as the mapping torus of the automorphism. Propertie
 s of the automorphism determine properties of the mapping torus and vice-v
 ersa. Gersten gave a simple example ψ:F3→F3ψ:F3→F3 of an automorphism whos
 e mapping torus is a 'poison subgroup' for nonpositive curvature\, in the 
 sense that any group containing F3⋊ψZF3⋊ψZ is not a CAT(0) group. In the o
 pposite direction\, Hagen-Wise and Button-Kropholler proved certain famili
 es of automorphisms have mapping tori that are cocompactly cubulated. We p
 rove that a large class of polynomially-growing free group automorphisms a
 dmitting an additional symmetry have CAT(0) mapping tori. The key tool is 
 a representation of these automorphisms as relative train track maps on or
 bigraphs\, certain graphs of groups thought of as orbi-spaces. This gives 
 a hierarchy for the mapping torus. It is an interesting question whether o
 r not our mapping tori are cocompactly cubulated.\n
DTSTART:20200129T200000Z
DTEND:20200129T210000Z
LOCATION:BURN 1104\, Burnside Hall\, CA\, QC\, Montreal\, H3A 0B9\, 805 rue
  Sherbrooke Ouest
SUMMARY:Rylee Lyman (Tufts University)
URL:/mathstat/channels/event/rylee-lyman-tufts-univers
 ity-312319
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