Let D be a digraph. A subset S of V (D) is a stable set if every pair of vertices in S is non-adjacent in D. A collection of disjoint paths is a path partition of D, if every vertex in V (D) is in exactly one path of .?We say that a stable set S and a path partition are orthogonal if each path of contains exactly one vertex of S. A digraph D satisfies the α-property if for every maximum stable set S of D, there exists a path partitionsuch that S and are orthogonal. A digraph D is α-diperfect if every induced subdigraph of D satisfies the α-property. In 1982, Berge proposed a characterization for α-diperfect digraphs in terms of forbidden anti-directed odd cycles. In 2018, Sambinelli, Silva and Lee proposed a similar conjecture. A digraph D satisfies the Begin-End-property or BE-property if for every maximum stable set S of D, there exists a path partition such that 1) S and are orthogonal and 2) for each path P ∈ , either the start or the end of P belongs to S. A digraph D is BE-diperfect if every induced subdigraph of D satisfies the BE-property. Sambinelli, Silva and Lee proposed a characterization for BE-diperfect digraphs in terms of forbidden
References
[1]
Bang-Jensen, J. and Gutin, G.Z. (2008) Digraphs: Theory, Algorithms and Applications. Springer Monographs in Mathematics. Springer, London. https://doi.org/10.1007/978-1-84800-998-1
[2]
Bondy, J.A. and Murty, U.S.R. (2008) Graph Theory, Volume 244 of Graduate Texts in Mathematics. Springer London, New York. https://doi.org/10.1007/978-1-84628-970-5
[3]
Berge, C. (1961) Färbung von graphen, deren sämtliche bzw. deren ungerade kreise starr sind. Wissenschaftliche Zeitschrift.
[4]
Chudnovsky, M., Robertson, N., Seymour, P. and Thomas, R. (2006) The Strong Perfect Graph Theorem. Annals of Mathematics, 51-229. https://doi.org/10.4007/annals.2006.164.51
[5]
Berge, C. (1981) Diperfect Graphs. 1-8. https://doi.org/10.1007/BFb0092250