The critical relations are the building blocks of the relational clone of a relational structure with respect to the relational operations intersection and direct product. In this paper we describe the critical relations of crowns. As a consequence, we obtain that the subpower membership problem for any crown is polynomial-time solvable.
Keywords: Clone; Critical relation; Crown; Finitely generated; Obstruction; Poset; Subpower membership problem.
© The Author(s) 2021.