Homotopy BV-algebra structure on the double cobar construction

TL;DR

This paper demonstrates that the double cobar construction of certain simplicial sets admits a homotopy BV-algebra structure, especially when the set is a double suspension or rational coefficients are used, using the Connes-Moscovici operator.

Contribution

It establishes conditions under which the double cobar construction has a homotopy BV-algebra structure, introducing a family of obstructions related to the antipode's involutivity.

Findings

Homotopy BV-algebra structure exists on double cobar construction for double suspensions.

Obstructions to the structure are characterized by specific algebraic operators.

The Connes-Moscovici operator defines the structure when the antipode is involutive.

Abstract

We show that the double cobar construction, $\Omega^2 C_*(X)$, of a simplicial set $X$ is a homotopy BV-algebra if $X$ is a double suspension, or if $X$ is 2-reduced and the coefficient ring contains the ring of rational numbers $\mathbb{Q}$. Indeed, the Connes-Moscovici operator defines the desired homotopy BV-algebra structure on $\Omega^2 C_*(X)$ when the antipode $S : \Omega C_*(X) \to \Omega C_*(X)$ is involutive. We proceed by defining a family of obstructions $O_n : \widetilde{C}_*(X) \to \widetilde{C}_*(X)^{\otimes n}$, $n\geq 2$ measuring the difference $S^2 - Id$. When $X$ is a suspension, the only obstruction remaining is $O_2 := E^{1,1} - \tau E^{1,1}$ where $E^{1,1}$ is the dual of the $\smile_1$-product. When $X$ is a double suspension the obstructions vanish.