Definition:Quadratic Functional

Definition

Let $B \sqbrk {x, y}$ be a bilinear functional.

Let $x = y$.

Then the functional $A \sqbrk x = B \sqbrk {x, x}$ is called a quadratic functional.

Sources

• 1963: I.M. Gelfand and S.V. Fomin: Calculus of Variations ... (previous) ... (next): $\S 5.24$: Quadratic Functionals. The Second Variation of a Functional