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Whenever $A$ is positivenegative semi-definite on the subspace of vectors $(a_1,\dots,a_n)$ with $\sum_i a_i=0$, then the same will be true for $B$. This is a result of Schoenberg.
Whenever $A$ is positive semi-definite on the subspace of vectors $(a_1,\dots,a_n)$ with $\sum_i a_i=0$, then the same will be true for $B$. This is a result of Schoenberg.
Whenever $A$ is negative semi-definite on the subspace of vectors $(a_1,\dots,a_n)$ with $\sum_i a_i=0$, then the same will be true for $B$. This is a result of Schoenberg.
Whenever $A$ is positive semi-definite on the subspace of vectors $(a_1,\dots,a_n)$ with $\sum_i a_i=0$, then the same will be true for $B$. This is a result of Schoenberg.
