THE FIRST JOHNSON SUBGROUPS ACT ERGODICALLY ON SU2-CHARACTER VARIETIES

We show that the first Johnson subgroup of the mapping class group of a surface Σ of genus greater than 1 acts ergodically on the moduli space of representations of π1(Σ) in SU2. Our proof relies on a local description of the latter space around the trivial representation and on the Taylor expansion of trace functions. 1. Introduction an