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0 votes
1 answer
71 views

Minimal size of a sumset over $\mathbb{F}_p$

Let $A, B \subseteq \mathbb{F}_p$ ($p$ a prime). How to show that $|A+B| \ge \min\{p, |A|+|B|-1\}$? Since $\mathbb{F}_p$ has only $p$ elements, $\forall S \subseteq \mathbb{F}_p, |S| \ge \min\{p, |S|\}...
keyboardAnt's user avatar
5 votes
1 answer
218 views

Sum-free sets in finite groups

Suppose $G$ is a group, $S \subset G$. Let’s call $S$ sum-free iff $\forall a, b \in S$ we have $ab \notin S$. Do there exist such $\epsilon > 0$, such that every sufficiently large finite group $G$...
Chain Markov's user avatar
  • 15.7k
4 votes
0 answers
138 views

Sidon sets in finite groups

Suppose $G$ is a group, $S \subset G$. Let’s call $S$ a Sidon subset iff $\forall$ quadruples $(a, b, c, d)$ of distinct elements of $S$ we have $ab \neq cd$ (named after Simon Sidon who studied such ...
Chain Markov's user avatar
  • 15.7k
1 vote
0 answers
88 views

Coset Progression is Freiman Isomorphic to Bohr Set

For an abelian group $G$, $H$ a finite subgroup of $G$, $x_1, \dots, x_r \in G$ and $L_1, \dots, L_r \in \mathbb N$, let: $P(x ; L) = P(x_1, \dots, x_r ; L_1, \dots, L_r) = \{l_1x_1 + \dots + l_rx_r ...
user366818's user avatar
  • 2,683
6 votes
1 answer
135 views

Subsets of $\mathbb Z/n\mathbb Z$ disjoint with some of its shifts

Are there any descriptions of all subsets $X$ of $\mathbb Z/n\mathbb Z$ with the following property: there exists $a\ne 0$ in $\mathbb Z/n\mathbb Z$ such that $X$ is disjoint with $X + a = \{x + a \...
Ilya V. Schurov's user avatar
2 votes
1 answer
48 views

Subsets of $\mathbb Z/n\mathbb Z$ that remain disjoint with themselves under shifts

Are there any descriptions of all subsets $X$ of $\mathbb Z/n\mathbb Z$ such that for any $a\ne 0$ in $\mathbb Z/n\mathbb Z$, $X$ is disjoint with $X + a = \{x + a \pmod n\mid x \in X\}$?
Ilya V. Schurov's user avatar