Galois actions on surfaces and a higher genus Grothendieck-Teichmüller group
We construct a modular operad $\mathbf{S}$ of mapping class groupoids modelling the higher-genus Teichmüller tower, with compositions and contractions encoding surface gluing. We prove a presentation theorem for maps out of $\mathbf{S}$ using genus-zero and genus-one generators and relations. Applying the work of Nakamura--Schneps, we obtain a faithful action of their subgroup $\widehatΓ\subseteq \widehat{\mathsf{GT}}$ on $\widehat{\mathbf{S}}$, and hence a faithful Galois action. The genus-zero truncation identifies with the cyclic operad of parenthesized ribbon braids, whose object-fixing profinite automorphism group is $\widehat{\mathsf{GT}}$. The completed classifying spaces form a modular $\infty$-operad whose corolla values are geometric étale homotopy types of moduli stacks of curves with nonzero tangent vectors at their marked points. The $\widehatΓ$-action induces a faithful action by homotopy automorphisms on the associated tower of profinite homotopy $1$-types, which agrees with the étale model in genus zero and one.