Mathematics
Within operator theory, Cooper worked in the area of linear operators on real or complex Hilbert spaces. He studied the unbounded operators that arose from quantum theory, extending basic work of Frigyes Riesz and John von Neumann.
Within transform theory, he worked on the representation and uniqueness of integral transforms, on approximation, and on linear transformations that satisfy functional relations arising from representations of linear groups. In this he collaborated closely with P.L. Butzer of RWTH Aachen.
Read more about this topic: Lionel Cooper (mathematician)