 Strictly copositive matrix (source code)

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= Strictly copositive matrix

A real <symmetric matrix> whose <quadratic form> is positive at every nonzero <vector> in the <nonnegative orthant>. By <compactness> of the nonnegative <unit sphere>, this is equivalent to a positive uniform lower bound $x^TAx\geq\delta\|x\|_2^2$ on that orthant. It need not be a <positive-definite matrix>.

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