Schwartz_space
Definition
A Schwartz space $\mathcal{S}$ is the function space of all functions whose derivatives are rapidly decreasing. This space has the important property that the Fourier transform is an automorphism on this space. This property enables one, by duality, to define the Fourier_transform for elements in the dual space $\mathcal{S}^{*}$ of $\mathcal{S}$, that is, for tempered_distributions. A function in the Schwartz space is sometimes called a Schwartz_function.