Let $X$ be a Banach space and $S$ a closed subset of $X$. Is the set $\tilde S=\{rs;\ s\in S,\ r\geq 0\}$ also closed?
2026-03-27 08:42:05.1774600925
A set under multiplication by non-negative real numbers in Banach space
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No. Take $S=(x=1)\subset\mathbb{R}^2$, for example