Atomic measure spaces and essentially normal composition operators
Raj Singh, T. Veluchamy · Bulletin of the Australian Mathematical Society · 1983
The adjoint of a composition operator CT on the L2-space of an atomic measure is computed and a characterization for an operator to be a composition operator is given in this short note. The dimensions of kernel and co-kernel of CT are calculated in order to characterise Fredholm composition operators. Finally, essentially normal composition operators are studied on l2.