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Nov 15, 2011 at 22:47 comment added Gerald Edgar A counterexample when $\alpha=\infty$. Let $X$ be uncountable with the discrete metric. Then a subset has either dimension $\infty$ (if uncountable) or $0$ (if countable). The only place finiteness of $\alpha$ is used in my answer is to get $X$ separable.
Nov 15, 2011 at 18:09 vote accept Ema
Nov 15, 2011 at 18:09
Nov 15, 2011 at 17:54 history edited Benoît Kloeckner CC BY-SA 3.0
Endollared the LaTeX.
Nov 15, 2011 at 15:48 comment added Tapio Rajala Answering my own question: Yes, $[0,1]\setminus \mathbb{Q}$ has this property.. by taking out an open set (union of open balls centered at the rational points) of Lebesgue measure less than $1$ we have a closed set of dimension $1$.
Nov 15, 2011 at 15:40 comment added Tapio Rajala For complete spaces $X$ this seems intuitively clear, but how about non-complete spaces? Does for example $[0,1]\setminus \mathbb{Q}$ have this property?
Nov 15, 2011 at 15:38 answer added Gerald Edgar timeline score: 18
Nov 15, 2011 at 14:58 comment added Pietro Majer @Igor: I don't see how what you say implies, for instance, the existence of a subset of $[0,1]$ of Hausdorff dimension say 1/2.
Nov 15, 2011 at 14:46 comment added Igor Rivin (unless you consider the dimension of the empty set to be undefined, in which case a one point set is a counterexample to the claim).
Nov 15, 2011 at 14:46 comment added Igor Rivin (unless the space itself has one point, in which case only the empty set works).
Nov 15, 2011 at 14:45 comment added Igor Rivin The empty set works, as does a 1-point set.
Nov 15, 2011 at 14:39 history asked Ema CC BY-SA 3.0