Operads of decorated cliques

Samuele Giraudo

Published 2017-02-01Version 1

The vector space of all polygons with configurations of diagonals is endowed with an operad structure. This is the consequence of a functorial construction $\mathsf{C}$ introduced here, which takes unitary magmas $\mathcal{M}$ as input and produces operads. The obtained operads involve regular polygons with configurations of arcs labeled on $\mathcal{M}$, called $\mathcal{M}$-decorated cliques and generalizing usual polygons with configurations of diagonals. We provide here a complete study of the operads $\mathsf{C}\mathcal{M}$. By considering combinatorial subfamilies of $\mathcal{M}$-decorated cliques defined, for instance, by limiting the maximal number of crossing diagonals or the maximal degree of the vertices, we obtain suboperads and quotients of $\mathsf{C}\mathcal{M}$. This leads to a new hierarchy of operads containing, among others, operads on noncrossing configurations, Motzkin configurations, forests, dissections of polygons, and involutions. We show that the suboperad of noncrossing configurations is Koszul and exhibit its presentation by generators and relations. Besides, the construction $\mathsf{C}$ leads to alternative definitions of several operads, like the operad of bicolored noncrossing configurations and the operads of simple and double multi-tildes.