Arithmetic group symmetry and finiteness properties of Torelli groups


We examine groups whose resonance varieties, characteristic varieties and Sigma-invariants have a natural arithmetic group symmetry, and we explore implications on various finiteness properties of subgroups. We compute resonance varieties, characteristic varieties and Alexander polynomials of Torelli groups, and we show that all subgroups containing the Johnson kernel have finite first Betti number, when the genus is at least $4$. We also prove that, in this range, the $I$-adic completion of the Alexander invariant is finite-dimensional, and the Kahler property for the Torelli group implies the finite generation of the Johnson kernel.


Alexandru Dimca

Institut Universitaire de France et Laboratoire J.A. Dieudonné, Université de Nice Sophia-Antipolis, Nice, France

Stefan Papadima

Simion Stoilow Institute of Mathematics, Bucharest, Romania