English

Almost-full transversals in equi-$n$-squares

Combinatorics 2024-12-11 v1

Abstract

In 1975, Stein made a wide generalisation of the Ryser-Brualdi-Stein conjecture on transversals in Latin squares, conjecturing that every equi-nn-square (an n×nn\times n array filled with nn symbols where each symbol appears exactly nn times) has a transversal of size n1n-1. That is, it should have a collection of n1n-1 entries that share no row, column, or symbol. In 2017, Aharoni, Berger, Kotlar, and Ziv showed that equi-nn-squares always have a transversal with size at least 2n/32n/3. In 2019, Pokrovskiy and Sudakov disproved Stein's conjecture by constructing equi-nn-squares without a transversal of size nlogn42n-\frac{\log n}{42}, but asked whether Stein's conjecture is approximately true. I.e., does an equi-nn-square always have a transversal with size (1o(1))n(1-o(1))n? We answer this question in the positive. More specifically, we improve both known bounds, showing that there exist equi-nn-squares with no transversal of size nΩ(n)n-\Omega(\sqrt{n}) and that every equi-nn-square contains nn1Ω(1)n-n^{1-\Omega(1)} disjoint transversals of size nn1Ω(1)n-n^{1-\Omega(1)}.

Cite

@article{arxiv.2412.07733,
  title  = {Almost-full transversals in equi-$n$-squares},
  author = {Debsoumya Chakraborti and Micha Christoph and Zach Hunter and Richard Montgomery and Teo Petrov},
  journal= {arXiv preprint arXiv:2412.07733},
  year   = {2024}
}

Comments

16 pages, 2 figures

R2 v1 2026-06-28T20:29:50.063Z