# Creation operators

A family of closed linear operators $\{ a^*(f) : f \in H \}$, where $H$ is some Hilbert space, acting in the Fock space constructed over $H$. They are the adjoints of the annihilation operators $\{ a(f) : f \in H \}$.
Cf. Annihilation operators for a precise description of the operators $a^*(f)$ and for suitable references.