Fringe pairs in generalized MSTD sets

TL;DR

This paper explores generalized MSTD sets, providing efficient constructions of multi-generational MSTD sets, analyzing their probabilistic properties, and studying interval decompositions into MSTD sets.

Contribution

It introduces efficient methods to construct k-generational MSTD sets and offers new proofs and probabilistic analyses of their properties.

Findings

Proved the positive proportion of sets with specific sum-difference properties.

Established that the ratio of logs of sum and difference sets concentrates around 1.

Identified a set with the highest known ratio of log |A+A| to log |A-A|.

Abstract

A More Sums Than Differences (MSTD) set is a set $A$ for which $|A+A|>|A-A|$. Martin and O'Bryant proved that the proportion of MSTD sets in $\{0,1,\dots,n\}$ is bounded below by a positive number as $n$ goes to infinity. Iyer, Lazarev, Miller and Zhang introduced the notion of a generalized MSTD set, a set $A$ for which $|sA-dA|>|\sigma A-\delta A|$ for a prescribed $s+d=\sigma+\delta$. We offer efficient constructions of $k$-generational MSTD sets, sets $A$ where $A, A+A, \dots, kA$ are all MSTD. We also offer an alternative proof that the proportion of sets $A$ for which $|sA-dA|-|\sigma A-\delta A|=x$ is positive, for any $x \in \mathbb{Z}$. We prove that for any $\epsilon>0$, $\Pr(1-\epsilon<\log |sA-dA|/\log|\sigma A-\delta A|<1+\epsilon)$ goes to $1$ as the size of $A$ goes to infinity and we give a set $A$ which has the current highest value of $\log |A+A|/\log |A-A|$. We also study decompositions of intervals $\{0,1,\dots,n\}$ into MSTD sets and prove that a positive proportion of decompositions into two sets have the property that both sets are MSTD.