Definition:Positive Definite Functional

Definition
Let $f : S \to T$ be a mapping.

Let $f \in \MM$, where $\MM$ stands for some function space.

Let $F \sqbrk f : \MM \to \R$ be a real-valued functional.

Suppose:


 * $\forall f \in \MM: F \sqbrk f > 0$

Then $F$ is a positive-definite functional.