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R. Jin showed that whenever A and B are sets of integers having positive upper Banach density, the sumset A+B is piecewise syndetic. This result was strengthened by Bergelson, Furstenberg, and Weiss to conclude that A+B must be piecewise…

Dynamical Systems · Mathematics 2010-11-02 John T. Griesmer

If $A$ and $B$ are subsets of an abelian group, their sumset is $A+B:=\{a+b:a\in A, b\in B\}$. We study sumsets in discrete abelian groups, where at least one summand has positive upper Banach density. Renling Jin proved that if $A$ and $B$…

Number Theory · Mathematics 2025-07-15 John T. Griesmer

Motivated by questions asked by Erdos, we prove that any set $A\subset{\mathbb N}$ with positive upper density contains, for any $k\in{\mathbb N}$, a sumset $B_1+\cdots+B_k$, where $B_1,\dots,B_k\subset{\mathbb N}$ are infinite. Our proof…

Dynamical Systems · Mathematics 2024-02-23 Bryna Kra , Joel Moreira , Florian K. Richter , Donald Robertson

Following their resolution of the Erd\H{o}s $B+B+t$ problem, Kra Moreira, Richter, and Robertson posed a number of questions and conjectures related to infinite configurations in positive density subsets of the integers and other amenable…

Combinatorics · Mathematics 2024-04-29 Ethan Ackelsberg

{The first version of this text was written and submitted to a journal on April, 12, 2018. This second version was submitted on April, 9, 2019.} We investigate the existence of subsets $A$ and $B$ of $\mathbb{N}:=\{0,1,2,\dots\}$ such that…

Number Theory · Mathematics 2019-12-24 Alain Faisant , Georges Grekos , Ram Krishna Pandey , Sai Teja Somu

For any set $A$ of natural numbers with positive upper Banach density and any $k\geq 1$, we show the existence of an infinite set $B\subset{\mathbb N}$ and a shift $t\geq0$ such that $A-t$ contains all sums of $m$ distinct elements from $B$…

Dynamical Systems · Mathematics 2025-09-16 Bryna Kra , Joel Moreira , Florian K. Richter , Donald Robertson

Every set $A$ of positive integers with upper Banach density 1 contains an infinite sequence of pairwise disjoint subsets $(B_i)_{i=1}^{\infty}$ such that $B_i$ has upper Banach density 1 for all $i \in \mathbf{N}$ and $\sum_{i\in I} B_i…

Number Theory · Mathematics 2020-04-17 Melvyn B. Nathanson

For a set $A \subset \mathbb{N}$ we characterize in terms of its density when there exists an infinite set $B \subset \mathbb{N}$ and $t \in \{0,1\}$ such that $B+B \subset A-t$, where $B+B : =\{b_1+b_2\colon b_1,b_2 \in B\}$. Specifically,…

Dynamical Systems · Mathematics 2024-04-22 Ioannis Kousek , Tristán Radić

In this article we describe all possible infinite linear configurations that can be found in a shift of any set of positive upper Banach density. This simultaneously generalizes Szemer\'edi's theorem on arithmetic progressions and the…

Dynamical Systems · Mathematics 2026-03-11 Felipe Hernández

We give a short proof of the fact that every set of natural numbers with positive upper Banach density contains the sum of two infinite sets. The approach simplifies earlier existing proofs.

Dynamical Systems · Mathematics 2026-03-31 Bryna Kra , Joel Moreira , Florian K. Richter , Donald Robertson

Erd\H{o}s conjectured that for any set $A\subseteq \mathbb{N}$ with positive lower asymptotic density, there are infinite sets $B,C\subseteq \mathbb{N}$ such that $B+C\subseteq A$. We verify Erd\H{o}s' conjecture in the case that $A$ has…

Number Theory · Mathematics 2016-05-06 Mauro Di Nasso , Isaac Goldbring , Renling Jin , Steven Leth , Martino Lupini , Karl Mahlburg

For any set $A$ of natural numbers with positive upper Banach density, we show the existence of an infinite set $B$ and sequences $(t_k)_{k\in \mathbb{N}}, (s_k)_{k\in \mathbb{N}}$ of natural numbers such that $\left\{ \sum_{n \in F}n : F…

Dynamical Systems · Mathematics 2025-10-22 Felipe Hernández , Ioannis Kousek , Tristán Radić

We show that for any set $A \subset \mathbb{N}$ with positive upper density and any $\ell,m \in \mathbb{N}$, there exist an infinite set $B\subset \mathbb{N}$ and some $t\in \mathbb{N}$ so that $\{mb_1 + \ell b_2 \colon b_1,b_2\in B\…

Dynamical Systems · Mathematics 2026-01-21 Ioannis Kousek

In this paper we show that every set $A \subset \mathbb{N}$ with positive density contains $B+C$ for some pair $B,C$ of infinite subsets of $\mathbb{N}$, settling a conjecture of Erd\H{o}s. The proof features two different decompositions of…

Combinatorics · Mathematics 2019-06-14 Joel Moreira , Florian Karl Richter , Donald Robertson

Renling Jin proved that if A and B are two subsets of the natural numbers with positive Banach density, then A+B is piecewise syndetic. In this paper, we prove that, under various assumptions on positive lower or upper densities of A and B,…

Number Theory · Mathematics 2017-08-09 Mauro Di Nasso , Isaac Goldbring , Renling Jin , Steven Leth , Martino Lupini , Karl Mahlburg

We answer two questions of Kra, Moreira, Richter and Robertson regarding the existence of infinite sumsets of the form $B + C$ in dense and sparse sets of integers and the relation of sumsets to sets of recurrence. We then further…

Dynamical Systems · Mathematics 2025-10-16 Luke Hetzel

Let $d(\cdot)$ denote the natural density on the positive integers. We characterize all sets $A,B$ with positive density satisfying $d(A+B)=d(A)+d(B)$, under the assumption that the two sets are not both contained in a proper finite union…

Number Theory · Mathematics 2026-04-15 Ethan Ackelsberg , Florian K. Richter

We show that every set $A$ of natural numbers with positive upper density can be shifted to contain the restricted sumset $\{b_1 + b_2 : b_1, b_2\in B \text{ and } b_1 \neq b_2 \}$ for some infinite set $B \subset A$.

Dynamical Systems · Mathematics 2023-11-07 Bryna Kra , Joel Moreira , Florian K. Richter , Donald Robertson

It was shown by V. Bergelson that any set B with positive upper multiplicative density contains nicely intertwined arithmetic and geometric progressions: For each positive integer k there exist integers a,b,d such that $ {b(a+id)^j:i,j…

Combinatorics · Mathematics 2014-02-26 Mathias Beiglböck

We investigate additive properties of sets $A,$ where $A=\{a_1,a_2,\ldots ,a_k\}$ is a monotone increasing set of real numbers, and the differences of consecutive elements are all distinct. It is known that $|A+B|\geq c|A||B|^{1/2}$ for any…

Combinatorics · Mathematics 2021-07-01 Imre Ruzsa , Jozsef Solymosi
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