Box and Nabla Products that are D-Spaces
Box and Nabla Products that are D-Spaces
A space $X$ is $D$ if for every assignment, $U$, of an open neighborhood to each point $x$ in $X$ there is a closed discrete $D$ such that $\bigcup \{U(x) : x \in D\}=X$. The box product, $\square X^\omega$, is $X^\omega$ with topology generated by all $\prod_n U_n$, where every …