Let ##u,v## be vectors in the same Euclidean space, and define the symmetric matrix ##M = uv'+vu'##, the sum of their two outer products.(adsbygoogle = window.adsbygoogle || []).push({});

I'm interested in whether or not ##M## is positive (semi)definite.

Does anybody know of any equivalent conditions that I might phrase "directly" in terms of the vectors ##u,v##?

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# Outer products & positive (semi-) definiteness

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