Problem with almost everywhere equality

Abstract

A topological space $Y$ is said to have (AEEP) if the following condition is fulfilled. Whenever $(X,\mathfrak{M})$ is a measurable space and $f,g:X\to Y$ are two measurable functions, then the set $\Delta (f,g)=\{x\in X:f(x)=g(x)\}$ is a member of $\mathfrak{M}$. It is shown that a metrizable space $Y$ has (AEEP) iff the cardinality of $Y$ is no greater than $2^{{\aleph }_0}$.

arXiv comment4 pages