For any two $n$-dimensional random vectors $X$ and $Y$, does the following inequality hold?
$$2 \mathrm{Cov}(X, Y) \preceq \mathrm{Cov}(X, X) + \mathrm{Cov}(Y, Y),$$
where $A \preceq B$ means $A - B$ is positive semi-definite.
Thanks!
For any two $n$-dimensional random vectors $X$ and $Y$, does the following inequality hold?
$$2 \mathrm{Cov}(X, Y) \preceq \mathrm{Cov}(X, X) + \mathrm{Cov}(Y, Y),$$
where $A \preceq B$ means $A - B$ is positive semi-definite.
Thanks!
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