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Aug 31, 2017 at 23:14 history bumped CommunityBot This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
Aug 1, 2017 at 23:04 comment added Henry.L @ChristianRemling Let me sit down and give it a second thought but thanks a lot!!
Aug 1, 2017 at 23:03 comment added Christian Remling I'm not sure a highbrow view is helpful here when there's the simple answer "exactly those $N$ that take the standard basis to a basis of ev's of $M$," and then you want only those that are also in $SO(n)$, or at least that's how I would approach it.
Aug 1, 2017 at 22:56 answer added paul garrett timeline score: 1
Aug 1, 2017 at 22:56 comment added Henry.L @ChristianRemling So there is not a specific way of characterizing all these $N$ besides checking if they actually fall in $SO(n)$?
Aug 1, 2017 at 22:50 comment added Christian Remling If $x_j$ are the normalized ev's of $M$, in any order (and written as columns), then you must take $N=(e^{i\alpha_1}x_1,\ldots, e^{i\alpha_n}x_n)$. So the final answer is: those $N$'s of this form that happen to be in $SO(n)$ (if any). If $M$ has multiple eigenvalues, this is still the answer, but you have more choices now.
Aug 1, 2017 at 22:46 comment added Christian Remling It's still not quite right, I think. For example, the $N$'s won't normally form a subgroup; $N=1$ typically won't work.
Aug 1, 2017 at 22:25 history edited Henry.L CC BY-SA 3.0
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Aug 1, 2017 at 14:11 history edited YCor
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Aug 1, 2017 at 13:21 history asked Henry.L CC BY-SA 3.0