Minimal Obstructions for Polarity, Monopolarity, Unipolarity and (s, 1)-Polarity in Generalizations of Cographs

Abstract

AbstractIt is known that every hereditary property can be characterized by finitely many minimal obstructions when restricted to either the class of cographs or the class of $$P_4$$ P 4 -reducible graphs. In this work, we prove that the same is true when restricted to some other superclasses of cographs, including $$P_4$$ P 4 -sparse and $$P_4$$ P 4 -extendible graphs (both of which extend $$P_4$$ P 4 -reducible graphs). We also present complete lists of $$P_4$$ P 4 -sparse and $$P_4$$ P 4 -extendible minimal obstructions for polarity, monopolarity, unipolarity, and (s, 1)-polarity, where s is a positive integer. In parallel to the case of $$P_4$$ P 4 -reducible graphs, all the $$P_4$$ P 4 -sparse minimal obstructions for these hereditary properties are cographs.