Hereditary Rigid Relations.
Abstract
An h-ary relation ρ on a finite set A is said to be hereditarily rigid if the unary partial functions on A that preserve ρ are the subfunctions of the identity map or of constant maps. A family of relations F is said to be hereditarily strongly rigid if the partial functions on A that preserve every ρ ∈ F are the subfunctions of projections or constant functions. In this paper we show that hereditarily rigid relations exist and we give a lower bound on their arities. We also prove that no finite hereditarily strongly rigid families of relations exist and we also construct an infinite hereditarily strongly rigid family of relations.