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May 10, 2021 at 9:10 history edited Duchamp Gérard H. E. CC BY-SA 4.0
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Aug 1, 2019 at 17:06 comment added Duchamp Gérard H. E. @ good hint (+1)
Aug 1, 2019 at 10:33 comment added Pietro Majer In fact, a commonly neglected fact is that the representation of an element $x$ of a Hilbert space as sum of its Fourier components in a Hilbert basis $\{u_\lambda\}_{\lambda\in\Lambda}$, namely $x=\sum_{\lambda\in\Lambda} (x\cdot u_\lambda)u_\lambda$, is always a summable family in $H$. Recalling this, the above false belief would just reduce to the very false "$\ell_1(\Lambda)=\ell_2(\Lambda)$" for any set $\Lambda$, that hopefully not many believe!
Feb 17, 2018 at 8:03 comment added Duchamp Gérard H. E. @RobertFurber Thank you for this learned description (+1)
Feb 17, 2018 at 7:44 comment added Robert Furber I particularly like Grothendieck's version of this. He proves that unconditional convergence is the same as absolute convergence for a locally convex space if and only if it is nuclear, i.e. every continuous linear map to a normed space is a nuclear map. The falsity of this belief then follows from the fact that a nuclear normed space is finite dimensional.
Dec 21, 2017 at 6:22 history edited Martin Sleziak CC BY-SA 3.0
MathJax - the question has been bumped anyway
Sep 20, 2017 at 3:41 history edited Duchamp Gérard H. E. CC BY-SA 3.0
Put "commutatively convergent" and "summable" withhin the text
Aug 9, 2017 at 2:02 history edited Duchamp Gérard H. E. CC BY-SA 3.0
Completed the answer
Aug 7, 2017 at 22:42 history edited Duchamp Gérard H. E. CC BY-SA 3.0
Recalled the definition of a summable family
Aug 7, 2017 at 19:26 history edited Martin Sleziak CC BY-SA 3.0
MathJax: \|
Aug 7, 2017 at 18:25 history edited Duchamp Gérard H. E. CC BY-SA 3.0
Formatting
S Aug 7, 2017 at 15:44 history answered Duchamp Gérard H. E. CC BY-SA 3.0
S Aug 7, 2017 at 15:44 history made wiki Post Made Community Wiki by Duchamp Gérard H. E.