Ultradistribution
In functional analysis, an ultradistribution (also called an ultra-distribution) is a generalized function that extends the concept of a distributions by allowing test functions whose Fourier transforms have compact support. They form an element of the dual space ๐ตโฒ, where ๐ต is the space of test functions whose Fourier transforms belong to ๐, the space of infinitely differentiable functions with compact support.