Given an abelian group $G$, a corner is a a subset of pairs of the form $(x,y),(x+g,y),(x,y+g)$ with $g$ non trivial. Ajtai and Szemerédi proved that, asymptotically for finite abelian groups, every dense subset $S$ of $G×G$ contains an corner.…
Given an abelian group $G$, a corner is a a subset of pairs of the form $(x,y),(x+g,y),(x,y+g)$ with $g$ non trivial. Ajtai and Szemerédi proved that, asymptotically for finite abelian groups, every dense subset $S$ of $G×G$ contains an corner.…