The Fredholm Theory of the Matrix
Phys. Rev. 91, 1524 – Published 15 September, 1953
DOI: https://doi.org/10.1103/PhysRev.91.1524
Abstract
The equation for the interaction representation transformation operator is put into integral form and the Fredholm theory of integral equations is used to give an explicit expression for the solution. No extension of the circle of convergence of the matrix seems possible in the general case.