Cellular chains on freehedra and operadic pairs

The paper is devoted to explaining the operadic meaning of freehedra, a family of polytopes originally defined to study free loop spaces. We introduce the notion of operadic pairs and algebras over them. Cellular chains on Stasheff associahedra and Stasheff multiplihedra assemble into a two-colored operadic pair that governs $A_\infty$-algebras and $A_\infty$-modules over them, with maps that are $A_\infty$ in both colors. An important quotient of this operadic pair is given by cellular chains on cubes and freehedra.