Disjoint Odd Cycles in Cubic Solid Bricks
Guantao Chen, Xing Feng, Fuliang Lu, Lianzhu Zhang · SIAM Journal on Discrete Mathematics · 2019
Carvalho, Lucchesi, and Murty [J. Combin. Theory Ser. B, 92 (2004), pp. 319--324, Theorem 3.5] presented a proof of a theorem of Reed and Wakabayashi that a brick G is nonsolid if and only if there exist two vertex-disjoint odd cycles C_1 and C_2 such that G-V(C_1 u̧p C_2) has a perfect matching. Consequently, every brick with no two vertex-disjoint odd cycles is solid. Recently, Lucchesi et al. [SIAM J. Discrete Math., 32 (2018), pp. 1478--1501] constructed infinite families of solid bricks containing two vertex-disjoint odd cycles. Noticing that none of these graphs is cubic, they conjectured that no cubic solid brick contains two vertex-disjoint odd cycles. In this note, we present an infinite family of graphs showing that this conjecture fails. We further show that the minimum counterexample is unique, which has 12 vertices.