English

Latin Squares whose transversals intersect in unusual ways

Combinatorics 2026-07-20 v1

Abstract

A latin square of order nn is an n×nn\times n array in which each of nn symbols occurs exactly once in each row and column. A transversal in such a square is a selection of nn entries that includes one representative of each row and column, and one of each symbol. For all even orders n28n\ge 28 except n=30n=30, we construct a latin square of order nn in which every pair of transversals share at least one entry. We conjecture that in our squares there is no single entry that is common to all transversals. We prove this conjecture for n10000n\le10\,000 by finding transversals using an algorithm that is likely to be of independent interest. We say that a transversal is dominant if it intersects every other transversal of the same latin square. We show that there exist latin squares of order nn that have a dominant transversal for n{5,7}n\in\{5,7\} and also for all n8n\ge8 such that n≢3mod4n\not\equiv3\bmod4.

Cite

@article{arxiv.2607.17547,
  title  = {Latin Squares whose transversals intersect in unusual ways},
  author = {Afsane Ghafari and Ian M. Wanless},
  journal= {arXiv preprint arXiv:2607.17547},
  year   = {2026}
}