Multivalued matrices and forbidden configurations

TL;DR

This paper investigates the maximum size of simple multivalued matrices avoiding certain forbidden submatrices, extending known results from binary matrices to multivalued cases and establishing bounds related to specific matrix families.

Contribution

It generalizes forbidden configuration results from binary to multivalued matrices and characterizes when the maximum size is polynomial or constant.

Findings

Forb(m,r,{}T_{}()) is a constant for certain matrix families.

Established conditions under which forb(m,r,{}T_{}(3)ackslash {}T_{}(2)) matches the growth of forb(m,2,{}F).

Most 2-columned F cases affirm the conjectured bounds.

Abstract

An $r$-matrix is a matrix with symbols in $\{0,1,\ldots,r-1\}$. A matrix is simple if it has no repeated columns. Let ${\cal F}$ be a finite set of $r$-matrices. Let $\hbox{forb}(m,r,{\cal F})$ denote the maximum number of columns possible in a simple $r$-matrix $A$ that has no submatrix which is a row and column permutation of any $F\in{\cal F}$. Many investigations have involved $r=2$. For general $r$, $\hbox{forb}(m,r,{\cal F})$ is polynomial in $m$ if and only if for every pair $i,j\in\{0,1,\ldots,r-1\}$ there is a matrix in ${\cal F}$ whose entries are only $i$ or $j$. Let ${\cal T}_{\ell}(r)$ denote the following $r$-matrices. For a pair $i,j\in\{0,1,\ldots,r-1\}$ we form four $\ell\times\ell$ matrices namely the matrix with $i$'s on the diagonal and $j$'s off the diagonal and the matrix with $i$'s on and above the diagonal and $j$'s below the diagonal and the two matrices with the roles of $i,j$ reversed. Anstee and Lu determined that $\hbox{forb}(m,r,{\cal T}_{\ell}(r))$ is a constant. Let ${\cal F}$ be a finite set of 2-matrices. We ask if $\hbox{forb}(m,r,{\cal T}_{\ell}(3)\backslash {\cal T}_{\ell}(2)\cup {\cal F})$ is $\Theta(\hbox{forb}(m,2,{\cal F}))$ and settle this in the affirmative for some cases including most 2-columned $F$.