Fundamental operator-function of an integro-differential operator with derivatives of functionals in Banach spaces

In this paper, we consider a generalized integro-differential operator with derivatives of functionals, which has in its construction an invertible operator in the linear part free of derivatives. The research uses previously obtained results in the field of fundamental operator functions in Banach spaces, as well as the properties of generalized functions, operators, and functionals. For an integro-differential operator with derivatives of functionals in Banach spaces, a fundamental operator-function in the terminology of Jordan sets is obtained and the conditions for the existence of this fundamental operator-function are revealed.

On Solvability in the Class of Distributions of Degenerate Integro-Differential Equations in Banach Spaces

The paper considers a new approach to constructing generalized solutions of degenerate integro-differential equations convolution type in Banach spaces. The principal idea of the method proposed implies the refusal of the condition of existence of the full Jordan set for the Fredholm operator of the higher derivative with respect to the operator bundle formed by the rest of operator coefficients of the differential part and by the operator kernel of the integral component of the equation. The conditions are superimposed upon the values of the operator function specially constructed on the basis elements of the Fredholm operator kernel. Under such an approach, the differential part of the equation may include not only the higher derivative but also any combination lower derivatives, what allows one to consider the convolution integral-differential equations from universal positions, without any special account of the structure of the structure of the operator bundle. The method proposed represents a form of generalization of the technique based on the application of Jordan sets of Fredholm operators, and in the case of existence of the latter the method coincides with this technique. The generalized solutions are constructed in the form of a convolution of the fundamental operator function, which corresponds to the equation under investigation, and a function, which includes the right-hand side of the equation and the initial data. The conditions, under which such a generalized solution does not contain any singular component, and the regular component converts the initial equation into an identity and satisfies the initial data, and the result will provide for the resolvability of the initial problem in the class of functions of characterized by the respective smoothness. In this case, the generalized solution constructed will be classical. The theorem on the form of fundamental operator function has been proved, the abstract results have been illustrated via examples of initialboundary value problems of applied character from the theory electromagnetic fields, the theory of oscillations in visco-elastic media, the theory of vibrations of thermal-elastic plates.

The Inverse Fundamental Operator Marching Method for Cauchy Problems in Range-Dependent Stratified Waveguides

The inverse fundamental operator marching method (IFOMM) is suggested to solve Cauchy problems associated with the Helmholtz equation in stratified waveguides. It is observed that the method for large-scale Cauchy problems is computationally efficient, highly accurate, and stable with respect to the noise in the data for the propagating part of a starting field. In further, the application scope of the IFOMM is discussed through providing an error estimation for the method. The estimation indicates that the IFOMM particularly suits to compute wave propagation in long-range and slowly varying stratified waveguides.

Robustness with respect to small delays for exponential stability of abstract differential equations in Banach spaces

This paper is concerned with robustness with respect to small delays for the exponential stability of abstract differential equations in Banach spaces. Some necessary and sufficient conditions are given in terms of the uniformly square integrability of the fundamental operator family and the uniform boundedness of its resolvent on the imaginary axis.