English

Multivalued forbidden numbers of two-rowed configurations -- the missing cases

Combinatorics 2025-02-10 v1

Abstract

The present paper considers extremal combinatorics questions in the language of matrices. An ss-matrix is a matrix with entries in {0,1,,s1}\{0,1,\ldots, s-1\}. An ss-matrix is simple if it has no repeated columns. A matrix FF is a configuration in a matrix AA, denoted FAF\prec A, if it is a row/column permutation of a submatrix of AA. Avoid(m,s,F)\text{Avoid}(m,s,F) is the set of mm-rowed, simple ss-matrices not containing a configuration of FF and forb(m,s,F)=max{A ⁣:AAvoid(m,s,F)}\text{forb}(m,s, F)=\max\{|A|\colon A \in \text{Avoid}(m,s,F)\}. Dillon and Sali initiated the systematic study of forb(m,s,F)\text{forb}(m,s, F) for 22-matrices FF, and computed forb(m,s,F)\text{forb}(m,s, F) for all 2-rowed FF when s>3s>3. In this paper we tackle the remaining cases when s=3s=3. In particular, we determine the asymptotics of forb(m,3,pK2)forb(m,3,pI2)\text{forb}(m,3,p\cdot K_2)-\text{forb}(m,3,p\cdot I_2) for p>3p>3, where K2K_2 is the 2×42\times 4 simple 22-matrix and I2I_2 is the 2×22\times 2 identity matrix, as well as the exact values of forb(m,3,F)\text{forb}(m,3,F) for many 2-rowed 22-matrices FF.

Keywords

Cite

@article{arxiv.2502.04741,
  title  = {Multivalued forbidden numbers of two-rowed configurations -- the missing cases},
  author = {Wallace Peaslee and Attila Sali and Jun Yan},
  journal= {arXiv preprint arXiv:2502.04741},
  year   = {2025}
}

Comments

19 pages

R2 v1 2026-06-28T21:35:50.295Z