Question about the Bolzano Weierstrass analogue in Hilbert spaces

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The discussion centers on the application of the Bolzano-Weierstrass theorem in the context of Hilbert spaces, specifically regarding its extension to infinite-dimensional spaces. The theorem asserts that in finite-dimensional vector spaces, a bounded sequence contains a convergent subsequence. However, it is established that this property does not hold in infinite-dimensional Hilbert spaces, as demonstrated by the sequence of standard basis vectors in the space \(\ell^2\), which does not contain a convergent subsequence.

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While reading a proof on the closure of the span of finite number vectors in a hilbert space with respect to the norm induced topology, I became stumped on a particular step of the proof using the Bolzano Weierstrass theorem.

For finite dimensional vector spaces, Bolzano Weierstrass states that:

"If ||an||<=M, then an contains a convergent subsequence (wrt whatever metric is defined on this vector space)"

Is it safe to assume that the above theorem extends to infinite dimensional vectors spaces (Hilbert spaces)?

Thanks!
 
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No, consider the sequence

(1,0,0,0,...)
(0,1,0,0,...)
(0,0,1,0,...)
...

in [itex]\ell^2[/itex].
 
Thanks for the really simple example!
 

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