Can Polynomials be positive definite?

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It seems to me that polynomial functions are ,trivially, not positive-definite (for definition )because of growth property of p.d functions. Am I right?

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Any positive definite function must satisfy $$ |f(t)| \leq |f(0)| \quad t \in \Bbb R $$ As you say, this is trivially never true for any non-constant polynomial function, since for any polynomial $f$, $\lim_{t \to \infty}|f(t)| = \infty$.