12–13 Sept 2025
UP FAMNIT
UTC timezone

Self separating properties of sets

13 Sept 2025, 14:30
20m
VP3 (UP FAMNIT)

VP3

UP FAMNIT

sekcija za mlade

Speaker

Maruša Lekše (Institute of Mathematics, Physics and Mechanics, Ljubljana)

Description

Let $G$ be a transitive permutation group of degree $n$. Let $\textbf{m}(G)$ be the largest integer such that, for every set $A$ of this size, we are guaranteed the existence of a permutation $g \in G$ such that $A\cap A^g$ is empty. By Neumann's Separation Lemma, we know that $\textbf{m}(G) \geq \sqrt{n}$. Experimental evidence suggests that, unless $G$ contains a large alternating subgroup, $\textbf{m}(G)$ grows asymptotically as $\mathcal{O}(\sqrt{n})$. We discuss for which families of permutation groups we can currently establish this expected bound.

This is joint work with Marco Barbieri, Kamilla Rekvényi and Primož Potočnik.

Authors

Kamilla Rekvényi Marco Barbieri Maruša Lekše (Institute of Mathematics, Physics and Mechanics, Ljubljana) Primož Potočnik

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