Connections between covers of $\mathbb Z$ and subset sums

TL;DR

This paper explores the relationship between covers of integers by residue classes and subset sums in fields, establishing conditions under which certain fractional sum sets contain arithmetic progressions.

Contribution

It introduces a novel connection between covers of integers and subset sums, demonstrating the existence of arithmetic progressions within specific fractional sum sets under certain conditions.

Findings

Fractional sum sets contain arithmetic progressions of length n_0

Conditions on covers and residue classes are sufficient for these progressions

Establishes a link between covers of integers and subset sum structures in fields

Abstract

In this paper we establish connections between covers of $\mathbb Z$ by residue classes and subset sums in a field. Suppose that $A_0=\{a_s(n_s)\}_{s=0}^k$ covers each integer at least $p$ times with the residue class $a_0(n_0)=a_0+n_0\mathbb Z$ irredundant, where $p$ is a prime not dividing any of $n_1,\ldots,n_k$. Let $m_1,\ldots,m_k\in\mathbb Z$ be relatively prime to $n_1,\ldots,n_k$ respectively. For any $c,c_1,\ldots,c_k\in\mathbb Z/p\mathbb Z$ with $c_1\cdots c_k\not=0$, we show that the set $$\bigg\{\bigg\{\sum_{s\in I}\frac{m_s}{n_s}\bigg\}:\, I\subseteq\{1,\ldots,k\} \ \mbox{and}\ \sum_{s\in I}c_s=c\bigg\}$$ contains an arithmetic progression of length $n_0$ with common difference $1/n_0$, where $\{x\}$ denotes the fractional part of a real number $x$.