Let
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be a vector space endowed with a norm
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. A norm is called
absolute if
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for all
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, where
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is applied componentwise and
monotone if
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whenever
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componentwise.
Norms having these properties are also called
Riesz norms; the two conditions are equivalent for finite-dimensional spaces (see
Horn and Johnson).
What about infinite-dimensional spaces? Does anyone have an example of a normed
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where the norm is satisfies one of the conditions but not the other? What about a function space?
For
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I think I have a proof that the two conditions are equivalent (by a handwavy appeal to Lebesgue's Dominated Convergence theorem). For function spaces, I suspect there's a counterexample. But this is all random 4am musing -- so please catch me if I'm disseminating lies!
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