$C-(k,\ell )$-Sum-Free Sets

Abstract

The Minkowski sum of two subsets $A$ and $B$ of a finite abelian group $G$ is defined as all pairwise sums of elements of $A$ and $B$: $A+B=\{a+b:a\in A,b\in B\}$. The largest size of a $(k,\ell )$-sum-free set in $G$ has been of interest for many years and in the case $G=\mathbb{Z}/n\mathbb{Z}$ has recently been computed by Bajnok and Matzke. Motivated by sum-free sets of the torus, Kravitz introduces the noisy Minkowski sum of two sets, which can be thought of as discrete evaluations of these continuous sumsets. That is, given a noise set $C$, the noisy Minkowski sum is defined as $A{+}_{C}B=A+B+C$. We give bounds on the maximum size of a $(k,\ell )$-sum-free subset of $\mathbb{Z}/n\mathbb{Z}$ under this new sum, for $C$ equal to an arithmetic progression with common difference relatively prime to $n$ and for any two element set $C$.