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Jan 2, 2018 at 15:45 history edited Schüler CC BY-SA 3.0
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Dec 2, 2017 at 8:18 history edited Schüler CC BY-SA 3.0
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Dec 1, 2017 at 18:40 comment added LSpice Your question doesn't quite make it clear, but you want a single $U$ that works for both $S_k$, right? (Otherwise I guess that @JochenGlueck's comment gives it immediately, modulo the $\sigma$-finiteness issue.)
Dec 1, 2017 at 15:39 vote accept Schüler
Dec 1, 2017 at 14:48 answer added Matthew Daws timeline score: 9
Dec 1, 2017 at 13:52 history edited Schüler CC BY-SA 3.0
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Dec 1, 2017 at 13:28 comment added Matthew Daws The answer will be negative if (and only if) you can find $S_1,S_2$ commuting, with $MS_i$ self-adjoint for both $i$, but with $MS_1$ not commuting with $MS_2$.
Dec 1, 2017 at 12:59 history edited Schüler CC BY-SA 3.0
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Dec 1, 2017 at 12:55 comment added Schüler I have edited my question.
Dec 1, 2017 at 12:53 history edited Schüler CC BY-SA 3.0
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Dec 1, 2017 at 12:52 history undeleted Schüler
Dec 1, 2017 at 10:33 history deleted Schüler via Vote
Dec 1, 2017 at 10:26 comment added Jochen Glueck Well, that depends. If $X$ can be chosen to be $\sigma$-finite, then $X$ can also be chosen to be finite by a simple change-of-density argument. However, I doubt that $X$ can always be chosen to be $\sigma$-finite in the spectral theorem (in particular, if $F$ is not separable). To be sure, I suggest to look it up in a textbook or a monograph where the spectral theorem is treated.
Dec 1, 2017 at 10:16 comment added Schüler Thank you. Do you mean that $\mu(X)$ can be equal to $\infty$?
Dec 1, 2017 at 10:11 comment added Jochen Glueck Your assumptions imply that $(MS)^* = S^*M = MS$, so $MS$ is self-adjoint, which shows that your claim is true, right? (I'm not quite convinced, however, that $(X,\mu)$ can be chosen as a ($\sigma$-)finite space, in particular if $F$ is not assumed to be separable.)
Dec 1, 2017 at 9:07 history asked Schüler CC BY-SA 3.0