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Oct 29, 2010 at 21:09 history edited Andrey Rekalo CC BY-SA 2.5
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Oct 29, 2010 at 21:04 history edited Bad English CC BY-SA 2.5
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Oct 28, 2010 at 21:54 history edited Bad English CC BY-SA 2.5
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Oct 28, 2010 at 21:20 comment added Bad English anon, in following answer i will try to describe common construction.
Oct 23, 2010 at 9:28 answer added Costabel timeline score: 2
Oct 22, 2010 at 0:45 comment added Yemon Choi My feeling is that this question may be related to the following one: is the set of normal, invertible operators on (separable) Hilbert space a group? There the answer is no, even for the finite-dimensional case, which makes me suspect that the answer to BA's original question is also no.
Oct 22, 2010 at 0:04 comment added anon Is A a map from H to H? By "automorphism in Banach-spaces sense," do you mean that A is a bounded and bijective linear map from H to H? In the definition of "realizable," is the "isomorphism" from H to the L^2 space a unitary from one Hilbert space to the other, or just an invertible linear map? What is the "direct image of A"? What does "realized" mean? Maybe your definition has the form: A is realizable if there is a map f [of some kind] from H to some L^2 space and a map g [of some kind: maybe a composition operator?] on the L^2 space with A = f^{-1} g f. Is this true? Please clarify.
Oct 21, 2010 at 21:39 history asked Bad English CC BY-SA 2.5