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Zeroes of the spectral density of the periodic Schrödinger operator with Wigner–von Neumann potential

Published online by Cambridge University Press:  13 December 2011

SERGUEI NABOKO
Affiliation:
Department of Mathematical Physics, Institute of Physics, Saint-Petersburg State University, Ulianovskaia 1, St. Petergoff, Saint-Petersburg, 198904Russia. e-mail: sergey.naboko@gmail.com
SERGEY SIMONOV
Affiliation:
Chebyshev Laboratory, Department of Mathematics and Mechanics, Saint-Petersburg State University, 14th Line, 29b, Saint-Petersburg, 199178Russia. e-mail: sergey.a.simonov@gmail.com

Abstract

We consider the Schrödinger operator α on the half-line with a periodic background potential and the Wigner–von Neumann potential of Coulomb type: csin(2ωx + δ)/(x + 1). It is known that the continuous spectrum of the operator α has the same band-gap structure as the free periodic operator, whereas in each band of the absolutely continuous spectrum there exist two points (so-called critical or resonance) where the operator α has a subordinate solution, which can be either an eigenvalue or a “half-bound” state. The phenomenon of an embedded eigenvalue is unstable under the change of the boundary condition as well as under the local change of the potential, in other words, it is not generic. We prove that in the general case the spectral density of the operator α has power-like zeroes at critical points (i.e., the absolutely continuous spectrum has pseudogaps). This phenomenon is stable in the above-mentioned sense.

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 2011

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