V. N. Sivkin | Searcharxiv

arXiv2026

A two-point phase recovering with spherical wave reference

We consider a reference wave, a radiation solution, and the sum of these solutions (total solution) for the Helmholtz equation in an exterior region. We give two-point formulas for approximate phase recovering of the radiation solution from the intensity of the total solution for the case of spherical reference wave. We show that these formulas can be used, in particular, for approximate phase recovering from holographic data on a single plane. By these formulas, we continue previous studies with plane wave reference.

math.AP↗

arXiv2025

Asymptotics of the spectra of the Dirichlet and Dirichlet-Neumann problems for the Sturm-Liouville equation with integral perturbation

The article studies the Dirichlet and Dirichlet-Neumann problems for the Sturm-Liouville equation perturbed by an integral operator with a convolution kernel. Sharp asymptotic formulas for the eigenvalues of these problems are found. The formulas contain information about the Fourier coefficients of the potential and the kernel, and estimates are obtained for the remainder terms of the asymptotics, which take into account both the rate of decrease as the eigenvvalues tend to infinity and the rate of decrease as the norms of the potential and kernel tend to zero. The formulas are also new in the case of the Sturm-Liouville operator, when the convolution kernel is zero.

math.SP↗