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Questions on the subject additive combinatorics, also known as arithmetic combinatorics, such as questions on: additive bases, sum sets, inverse sum set theorems, sets with small doubling, Sidon sets, Szemerédi's theorem and its ramifications, Gowers uniformity norms, etc. Often combined with the top-level tags nt.number-theory or co.combinatorics. Some additional tags are available for further specialization, including the tags sumsets and sidon-sets.

11 votes
1 answer
731 views

What is the smallest cardinality of a set A whose difference A-A contains $n$ consequtive in...

Problem. What is the smallest cardinality $d(n)$ of a set $A$ of integer numbers such that the difference set $A-A=\{a-b:a,b\in A\}$ contains $n$ consequtive integer numbers? It can be shown that $(1 …
Taras Banakh's user avatar
  • 41.8k
4 votes
1 answer
154 views

Difference bases in simple cyclic groups

A subset $B$ of an abelian group $G$ is called a difference-basis if $B-B=G$. For a finite group $G$ by $\Delta(G)$ we denote the smallest cardinality of a difference basis of $G$. Let $C_n=\{z\in\ma …
Taras Banakh's user avatar
  • 41.8k
12 votes
2 answers
890 views

Factorizable groups

Definition. A finite group $G$ is factorizable if for any positive integer numbers $a,b$ with $ab=|G|$ there are subsets $A,B\subset G$ of cardinality $|A|=a$ and $|B|=b$ such that $AB=G$. Problem 1. …
Taras Banakh's user avatar
  • 41.8k
11 votes
0 answers
531 views

Cyclic and prime factorizations of finite groups

A tuple $(A_1,\dots,A_n)$ of subsets of a finite group $G$ is called a factorization of $G$ if $G=A_1\cdots A_n$ and $|A_1|\cdots|A_n|=G$. In Cryptology factorizations of groups are known as logarit …
Taras Banakh's user avatar
  • 41.8k
7 votes
3 answers
496 views

Product-one sets in non-commutative groups

A nonempty subset $D$ of a group $G$ is called $\bullet$ decomposable if $D\subseteq DD$, that is every element $x\in D$ is can be written as the product $x=yz$ of some elements $y,z\in D$; $\bullet$ …
Taras Banakh's user avatar
  • 41.8k
5 votes

Is each finite group multifactorizable?

I've just discovered that the alternating group $A_4$ is not multifactorizable. Namely, it can not be written as the product $A_4=ABC$ of subsets $A,B,C\subset A_4$ of cardinality $|A|=2$, $|B|=3$, an …
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  • 41.8k
1 vote
0 answers
72 views

Unit-product sets in finite decomposable sets in groups

A non-empty subset $D$ of a group is called decomposable if each element $x\in D$ can be written as the product $x=yz$ for some $y,z\in D$. Problem. Let $D$ be a finite decomposable subset of a gr …
Taras Banakh's user avatar
  • 41.8k
3 votes
0 answers
136 views

A question on a result of Imre Ruzsa concerning sum-sets

Th main result of this preprint of Imre Ruzsa implies the following Corollary (Ruzsa): For every $r\in\mathbb N$ there exists a real number $\alpha<1$ and a positive integer $m$ such that for ever …
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0 votes

Product-one sets in non-commutative groups

This is not an answer, but too long for a comment. Below I write down some conditions (on a group or a decomposable set) guaranteeing that a decomposable set in a group is product-one. Proposition 1. …
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  • 41.8k
3 votes
Accepted

Product-one sets in non-commutative groups

GAP shows that the groups SmallGroup(27,3), SmallGroup(27,4), SmallGroup(36,11), SmallGroup(39,1) SmallGroup(48,3) do contain many 5-element decomposable sets, which are not product-one. So, the lower …
Taras Banakh's user avatar
  • 41.8k
2 votes

Large product-1-free sets in finite groups

Realizing the idea of @NickGill we shall confirm the lower bound for solvable groups with five exceptions of the groups $G$ isomorphic to the groups $C_3,C_5,C_3\times C_3, D_{10}$ and $(C_3\times C_ …
Taras Banakh's user avatar
  • 41.8k
3 votes
3 answers
473 views

Large product-1-free sets in finite groups

$\DeclareMathOperator\SmallGroup{SmallGroup}$Definition. A subset $A$ of a group $G$ is called product-1-free if for any sequence of pairwise distinct elements $a_1,\dots,a_n$ of $A$ the product $a_1\ …
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  • 41.8k
0 votes

Large product-1-free sets in finite groups

For finite solvable groups $G$ we have the following lower bound for the number $f_1(G)$. Theorem. Let $G$ be a finite solvable group of cardinality $|G|=\prod_{k=1}p_k$ for some prime numbers $p_1,\d …
Taras Banakh's user avatar
  • 41.8k
11 votes
3 answers
563 views

Is each finite group multifactorizable?

Definition. A finite group $G$ is called multifactorizable if for any positive integer numbers $a_1,\dots,a_n$ with $a_1\cdots a_n=|G|$ there are subsets $A_1,\dots,A_n\subset G$ such that $A_1\cdots …
Taras Banakh's user avatar
  • 41.8k
5 votes
0 answers
114 views

$m$-thick sets with small $n$-fold sumsets in finite cyclic groups

Problem. Is it true that for every positive integers $n,m$ there exists a subset $A_{n,m}$ of a finite cyclic group $G$ having the following two properties: $(\Sigma_n)$ the $n$-fold sum $A_{n,m}^{+ …
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