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Feb 26, 2018 at 15:36 comment added Mateus Araújo On a second thought, the proof did require me to consider $\|1^{(n)}\|$ for all $n$, so it was incorrect. I rewrote it so that it now applies for all dimensions larger or equal to $3$. Thanks for the heads-up.
Feb 26, 2018 at 15:33 history edited Mateus Araújo CC BY-SA 3.0
added 244 characters in body
Feb 25, 2018 at 22:20 comment added Mateus Araújo "e.g." means "for example". But no, you cannot insert $1^{(4)}$ if you're talking about norms in $\mathbb R^3$. Why would you?
Feb 25, 2018 at 20:56 comment added Lutz Mattner Then we must have $n=3$, and you can't insert $1^{(4)}$.
Feb 25, 2018 at 19:47 comment added Mateus Araújo Sure I can. I'm using the convention that e.g. $\|(a,b)\| := \|(a,b,0)\|$. Just pad the vectors with zeroes.
Feb 25, 2018 at 17:58 comment added Lutz Mattner But then you cannot, as in your answer, insert $1^{(n)}$ for different $n$.
Feb 25, 2018 at 17:43 comment added Mateus Araújo Indeed, it doesn't make any sense, so that's why I'm not talking about an arbitrary normed space. I thought the question already made clear that I'm talking about a fixed norm in $\mathbb R^n$.
Feb 24, 2018 at 12:52 comment added Lutz Mattner Where are your norms defined? In an arbitrary normed space, permutation-invariance of the norm, or disjointness of the supports of vectors, just don't make sense. And perhaps you are considering some family of norms on different spaces without saying so?
Feb 24, 2018 at 9:24 history edited Mateus Araújo CC BY-SA 3.0
deleted unnecessary assumption
Feb 23, 2018 at 16:39 vote accept Mateus Araújo
Feb 23, 2018 at 15:48 history answered Mateus Araújo CC BY-SA 3.0