The finiteness of the discrete spectrum of a model operator associated with a system of three particles on a lattice

We consider a model operator H associated with a system of three particles on a lattice interacting via nonlocal pair potentials. Under some natural conditions on the parameters specifying this model operator H, we prove the finiteness of its discrete spectrum.     

Essential spectrum of a model operator associated with a three-particle system on a lattice

We consider a model operator H associated with the system of three particles interacting via nonlocal pair potentials on a ν-dimensional lattice. We identify channel operators and use their spectra to describe the position and structure of the essential spectrum of H. We obtain an analogue of the Faddeev equation for the eigenfunctions of H.     

The essential spectrum of the three-particle discrete operator corresponding to a system of three fermions on a lattice

We consider a family of three-particle discrete Shrödinger operators H _μ (K). These operators are associated with the Hamiltonian for a system of three identical particles (fermions) with pairwise two-particle interactions on neighboring junctions of the d-dimensional lattice Z ^d . We describe the location and the structure of the essential spectrum of the operator H _μ (K) for all values of the three-particle quasi-momentum K ∈ T ^d and the interaction energy μ > 0.     

Asymptotics of the discrete spectrum of a perturbed Hill operator

One considers a perturbed one-dimensional Hill operator. One gives a formula for the asymptotics of the discrete spectrum in the gap of the continuous spectrum and conditions under which this formula is valid.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 147, pp. 188–189, 1985.In conclusion the author expresses his deep gratitude to his scientific adviser M. Sh. Birman for the formulation of the problem and for his constant interest in this note.     

Asymptotics of the discrete spectrum for a radial Schrödinger operator with nearly Coulomb potential

The radial Schrödinger equation with Coulomb potential perturbed on a compact set is considered. An asymptotic formula for the discrete spectrum is obtained. It follows from this formula that the quantum defect tends to a constant when the principal quantum number tends to infinity. An explicit expression of this constant through the perturbation is obtained.     

Asymptotics of the spectrum of the Sturm-Liouville operator with regular boundary conditions

On the interval (0, π), we consider the spectral problem generated by the Sturm-Liouville operator with regular but not strongly regular boundary conditions. For an arbitrary potential q(x) ∈ L ₁ (0, π) [q(x) ∈ L ₂(0, π)], we establish exact asymptotic formulas for the eigenvalues of this problem.     

Estimates of the discrete spectrum of a linear operator pencil

Based on the direct methods of the perturbation theory, sufficient conditions for the finiteness of the discrete spectrum of linear pencils of the form L(λ)=B−λA, where A and B are bounded self-adjoint operators, are established. An estimate formula for the discrete spectrum is also presented. As applications, we study the spectrum of the characteristic equation of radiation energy transfer.     

Asymptotics of the spectrum of a second-order nonselfadjoint degenerate elliptic differential operator on the interval

Some properties are studied of a degenerate elliptic operator P defined on the interval (0, 1); namely, the resolvent of P is estimated. The completeness is investigated of the system of vector functions of P, and the summability is studied by the Abel method with parentheses of the Fourier series of elements in the corresponding Hilbert spaces with respect to systems of the root vector functions of P. An asymtotic formula is obtained for the distribution of the eigenvalues of P that distinguishes the principal term of the asymptotics.     

On the discrete spectrum of a perturbed Wiener-Hopf integral operator

Translated from Matematicheskie Zametki, Vol. 51, No. 1, pp. 102–113, January, 1992.     

Asymptotics of the spectrum of the Laplace operator on Riemannian Sol-manifolds in the adiabatic limit

We obtain the adiabatic asymptotics of the distribution function of the spectrum of the Laplace operator on a Riemannian Sol-manifold with a one-dimensional invariant foliation.     

The discrete spectrum in the gaps of a second-order perturbed periodic operator

Leningrad State University. Translated from Funktsional'nyi Analiz i Ego Prilozheniya, Vol. 25, No. 2, pp. 89–92, April–June, 1991.     

On the discrete spectrum of a perturbed periodic Schrödinger operator

A perturbed periodic Schrödinger operator is considered. Conditions on the perturbation are obtained, under which the discrete spectrum in the gap is finite or, on the contrary, is infinite. In the latter case there are given formulas for the asymptotic behavior of the eigenvalues with respect to the index and conditions under which these formulas hold. The results are formulated in terms of a model problem.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 190, pp. 157–162, 1991.In conclusion the author expresses his gratitude to his scientific adviser M. Sh. Birman.     

Asymptotics of the spectrum and eigenfunctions of the magnetic induction operator on a compact two-dimensional surface of revolution

Magnetic fields in conducting liquids (in particular, magnetic fields of galaxies, stars, and planets) are described by the magnetic induction operator. In this paper, we study the spectrum and eigenfunctions of this operator on a compact two-dimensional surface of revolution. For large magnetic Reynolds numbers, the asymptotics of the spectrum is studied; equations defining the eigenvalues (quantization conditions) are obtained; and examples of spectral graphs near which these points are located are given. The spatial structure of the eigenfunctions is studied.