Dynamics and polynomial invariants of free-by-cyclic groups

Dynamics and polynomial invariants of free-by-cyclic groups

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Ilya Kapovich, University of Illinois
Fine Hall 314

The theory developed by Thurston, Fried and McMullen provides a near complete picture of the various ways a hyperbolic 3-manifold M can fiber over the circle. Namely, there are distinguished convex cones in the first cohomology H^1(M;R) whose integral points all correspond to fibrations of M, and the dynamical features of these fibrations are all encoded by McMullen's "Teichmuller polynomial." This talk will describe recent work developing aspects of this picture in the setting of a free-by-cyclic group G (the mapping torus group of an automorphism of a finite rank free group). Specifically, we will describe a polynomial invariant that determines a convex polygonal cone C in the first cohomology of G whose integral points all correspond to algebraically and dynamically interesting splittings of G. The polynomial invariant additionally provides a wealth of dynamical and algebraic information about these splittings. This is joint work with Spencer Dowdall and Christopher Leininger.