Primary and Branched Solutions in the Problem of Approximation of a Finite Function by the Modulus of Double Discrete Fourier Transform

We study the problem of nonuniqueness of solutions for one class of Hammerstein-type nonlinear integral equations appearing in the problems of approximation of a finite function of two variables by the modulus of the double discrete Fourier transform. We establish the existence and properties of real (primary) solutions of four types and perform numerical investigations of branching of primary solutions of the second type. We also determine the efficiency of real and branched complex solutions.