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May 27, 2023 at 11:09 comment added The Amplitwist The tinyurl link in a comment above points to a Google Books search for "Aronhold polarisation" in the mentioned book by Procesi (Zbl 1154.22001). (Leaving this comment because URL shorteners can easily break, so they should be avoided whenever possible.)
Jan 10, 2012 at 22:25 vote accept asllearner
Jan 10, 2012 at 0:47 comment added asllearner I see. wow. Thanks. grand hat tip. Sorry to be so peevish....just what I needed. I will check out procesi...
Jan 10, 2012 at 0:47 vote accept asllearner
Jan 10, 2012 at 22:25
Jan 9, 2012 at 17:48 comment added Vladimir Dotsenko I actually overlooked that you complained about the available links and asked for textbooks. A reference I like is Procesi, "Lie groups: an approach through invariants and representations", section on Aronhold method. (It is available on Google Books, tinyurl.com/aronhold - check it out.)
Jan 9, 2012 at 17:33 comment added Vladimir Dotsenko 2. A $4$-dimensional vector space $V$ over real numbers is isomorphic to $\mathbb{R}^4$. If, incidentally, the vector space $V$ is an algebra, you can take the algebra structure with you via an isomorphism of your choice, right? ;-)
Jan 9, 2012 at 17:30 comment added Vladimir Dotsenko 1. In various contexts related to identities in the noncommutative/nonassociative settings this is quite standard. Check, e.g. the MO question mathoverflow.net/questions/61884/… and the Wikipedia article en.wikipedia.org/wiki/Homogeneous_function#Polarization - to name just two of zillions.
Jan 9, 2012 at 16:42 comment added asllearner thank you. I get your general point. I have never seen this discussed in any textbook I have read, so I am wondering where it comes from. This is probably a really stupid question...if $x$ is a matrix with entries in $\mathbb{R}$ is it an element of $\mathbb{R}^4$? isn't an element of $\mathbb{R}^4$ a vector (e.g. four-vector with real entries)--yes technically a matrix, but you cant take powers of it...or can you!?
Jan 9, 2012 at 14:07 history answered Vladimir Dotsenko CC BY-SA 3.0