Monochromatic sumsets in countable colourings of abelian groups

Autorzy

Dane publikacji

  • DOI: 10.4064/ba240807-24-11

  • Tom 72

  • Zeszyt 2

  • Czasopismo: Bulletin of the Polish Academy of Sciences Mathematics

  • Strony: 97-102

  • Data publikacji online: 17.12.2024

Liczba wyświetleń: 0

Liczba pobrań: 0

Abstrakt

Fernández-Bretón, Sarmiento and Vera showed that whenever a direct sum of sufficiently many copies of $\mathbb Z_4$, the cyclic group of order 4, is countably coloured there are arbitrarily large finite sets $X$ whose sumsets $X+X$ are monochromatic. They asked if the elements of order 4 are necessary, in the following strong sense: if $G$ is an abelian group having no elements of order 4, is it always the case that there is a countable colouring of $G$ for which there is not even a monochromatic sumset $X+X$ with $X$ of size 2? Our aim in this short note is to show that this is indeed the case.