Action of the Johnson-Torelli group on representation varieties

William M. Goldman, Eugene Z. Xia
2012 Proceedings of the American Mathematical Society  
Let Σ be a compact orientable surface with genus g and n boundary components B = (B 1 , . . . , B n ). Let c = (c 1 , . . . , c n ) ∈ [−2, 2] n . Then the mapping class group MCG of Σ acts on the relative SU(2)-character variety X C := Hom C (π, SU(2))/SU (2) , comprising conjugacy classes of representations ρ with tr(ρ(B i )) = c i . This action preserves a symplectic structure on the smooth part of X C , and the corresponding measure is finite. Suppose g = 1 and n = 2. Let J ⊂ MCG be the
more » ... oup generated by Dehn twists along null homologous simple loops in Σ. Then the action of J on X C is ergodic for almost all c.
doi:10.1090/s0002-9939-2011-10972-9 fatcat:jyb6n6fujbggdpfcnb6sgyj4fq