English

Small $q$-kernels in digraphs

Combinatorics 2026-08-01 v1

Abstract

We address three questions of Spiro [Europ. J. Combin., 133:Paper No. 104307, 2026] on smallest qq-kernels in digraphs. All three questions are on the existence of small qq-kernels in digraphs, where 'smallness' is measured in different ways. We answer one of these questions in the affirmative, and the other two in the negative. We further study the latter two questions in the context of bipartite digraphs. In particular, we show that in the bipartite setting, the answer to one of the two questions is affirmative if and only if qq is odd. For the other question, we show that the answer is positive when the digraph is bipartite and qq is odd (the case when the digraph is bipartite and qq is even remains open).

Cite

@article{arxiv.2608.00825,
  title  = {Small $q$-kernels in digraphs},
  author = {Irena Penev and Maya Stein and Ana Trujillo-Negrete},
  journal= {arXiv preprint arXiv:2608.00825},
  year   = {2026}
}

Comments

10 pages, 3 figures