Syntactic aspects of hypergraph polytopes

Jovana Obradovic (1) , Pierre-Louis Curien (2) , Jelena Ivanovic (3)

1 IRIF (UMR_8243) - Institut de Recherche en Informatique Fondamentale
2 PI.R2 - Design, study and implementation of languages for proofs and programs
3 University of Belgrade [Belgrade]

This paper introduces an inductively defined tree notation for all the faces of polytopes arising from a simplex by truncations, that allows us to view inclusion of faces as the process of contracting tree edges. Our notation instantiates to the well-known notations for the faces of associahedra and permutohedra. Various authors have independently introduced combina-torial tools for describing such polytopes. We build on the particular approach developed by Došen and Petric, who used the formalism of hypergraphs to describe the interval of polytopes from the simplex to the permutohedron. This interval was further stretched by Petric to allow truncations of faces that are themselves obtained by truncations, and iteratively so. Our notation applies to all these polytopes. We illustrate this by showing that it instantiates to a notation for the faces of the permutohedron-based associahedra, that consists of parenthesised words with holes. The paper also explores links between poly-topes and categorified operads. Došen and Petri´cPetri´c have exhibited some families of hypergraph polytopes (associahedra, permutohedra, and hemiassociahedra) describing the coherences, and the coherences between coherences etc., arising by weakening sequential and parallel associativity of operadic composition. We complement their work with a criterion allowing us to recover the information whether edges of these " operadic polytopes " come from sequential, or from parallel associativity. We also give alternative proofs for some of the original results of Došen and Petric.

Domaines: Mathématiques [math]; Catégories et ensembles [math.CT]; Combinatoire [math.CO]

Jovana Obradovic, Pierre-Louis Curien, Jelena Ivanovic. Syntactic aspects of hypergraph polytopes. Journal of Homotopy and Related Structures, inPress. ⟨hal-01669490⟩