Spectral Theory

The Asymptotic Behavior of the Solutions of the Wave Equation Concentrated near the Axis of a Two-Dimensional Waveguide in an Inhomogeneous Medium.- §1. A Waveguide in an Inhomogeneous Medium.- §2. The Construction of the Solutions of the Wave Equation Concentrated near the Waveguide Axis.- §3. The Asymptotic Behavior of the Eigenfunctions and Eigenvalues of the Boundary Problem for the Waveguide.- Literature Cited.- Perturbations of the Spectrum of the Schroedinger Operator with a Complex Periodic Potential.- §1. Preliminary Information.- §2. Investigations of the Perturbed Operator.- §3. Investigation of the Spectrum under the Condition $$/int{/left| /text{q}/left( /text{x} /right) /right|}{{/text{e}}^{/text{ }/!/!/delta/!/!/text{ }/left| x /right|}}dx$$ < ?.- §4. Proof That There Are No Eigenvalues on the Continuous Spectrum.- Literature Cited.- The Discrete Spectra of the Dirac and Pauli Operators.- §1. Auxiliary Information.- §2. The Discrete Spectrum of the Dirac Operator in the Case of Spherical Symmetry.- §3. The Discrete Spectrum of the Dirac Operator in the Three-Dimensional Case.- §4. The Discrete Spectrum of the Pauli Operator.- Literature Cited.- The Nonself-Adjoint Schroedinger Operator. III.- §1. Auxiliary Information.- §2. The Operator with Potential q(x) ? S?.- §3. The Operator with Potential q(x) ? Sn, n < ?.- Literature Cited.- The Singular Numbers of the Sum of Completely Continuous Operators.- Literature Cited.- Double-Integral Operators in the Ring R^.- Literature Cited.- Correction to “The Inverse Problem in the Theory of Seismic Wave Propagation”.