Timeline for Commutant of a von Neumann algebra as the linear span of unitaries.
Current License: CC BY-SA 3.0
4 events
| when toggle format | what | by | license | comment | |
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| Dec 4, 2012 at 19:43 | answer | added | Mark Tomforde | timeline score: 6 | |
| Oct 17, 2012 at 15:33 | comment | added | Jason Ekstrand | Thanks Jonas. Murphy showed decomposition into hermitian elements and into positive elements and that has been used heavily in the last chapter. However, I don't recall coming across that decomposition into unitaries (and I have done all the HW problems). Thanks for providing it, I figured I was missing something simple. | |
| Oct 16, 2012 at 22:06 | comment | added | Jonas Meyer | Does Murphy show in a previous chapter (perhaps an exercise) that in a unital C*-algebra, every element is a linear combination of 4 unitary elements? (If $x=x^*$ and $\|x\|\leq 1$, then $x\pm i\sqrt{1-x^2}$ are unitary and $x$ is their average$.) $A'$ is a unital C*-algebra. | |
| Oct 16, 2012 at 21:19 | history | asked | Jason Ekstrand | CC BY-SA 3.0 |