Real moduli space of stable rational curves revisted

Cornell University , 2019. № 1905.04499.

Khoroshkin A., Willwacher T.

We give a description of the operad formed by the real locus of the moduli space of stable genus zero curves with marked points $\overline{{\mathcal M}_{0,{n+1}}}({\mathbb R})$ in terms of a homotopy quotient of an operad of associative algebras. We use this model to find different Hopf models of the algebraic operad of Chains and homologies of $\overline{{\mathcal M}_{0,{n+1}}}({\mathbb R})$. In particular, we show that the operad $\overline{{\mathcal M}_{0,{n+1}}}({\mathbb R})$ is not formal. The manifolds $\overline{{\mathcal M}_{0,{n+1}}}({\mathbb R})$ are known to be Eilenberg-MacLane spaces for the so called pure Cacti groups.  As an application of the operadic constructions we prove that for each $n$ the cohomology ring $H^{\udot}(\overline{{\mathcal M}_{0,{n+1}}}({\mathbb R}),{\mathbb{Q}})$ is a Koszul algebra and that the manifold $\overline{{\mathcal M}_{0,{n+1}}}({\mathbb R})$ is not formal but is a rational $K(\pi,1)$ space. We give the description of the Lie algebras associated with the lower central series filtration of the pure Cacti groups.  

Keywords: пространства модулей комплексных кривых, operad, операда, moduli spaces of curves