Galvin's problem in higher dimensions

Abstract

It is proved that for each natural number $n$, if $\left|\mathbb{R}\right|={\aleph }_n$, then there is a coloring of ${\left[\mathbb{R}\right]}^{n+2}$ into ${\aleph }_0$ colors that takes all colors on ${\left[X\right]}^{n+2}$ whenever $X$ is any set of reals which is homeomorphic to $\mathbb{Q}$. This generalizes a theorem of Baumgartner and sheds further light on a problem of Galvin from the 1970s. Our result also complements and contrasts with our earlier result saying that any coloring of ${\left[\mathbb{R}\right]}^2$ into finitely many colors can be reduced to at most $2$ colors on the pairs of some set of reals which is homeomorphic to $\mathbb{Q}$ when large cardinals exist.

6 pages, submitted