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Absence of high-energy spectral concentration for Dirac systems with divergent potentials

Published online by Cambridge University Press:  12 July 2007

M. S. P. Eastham
Affiliation:
Department of Computer Science, Cardiff University, PO Box 916, Cardiff CF24 3XF, UK
K. M. Schmidt
Affiliation:
School of Mathematics, Cardiff University, Cardiff CF24 4AG, UK([email protected])

Abstract

It is known that one-dimensional Dirac systems with potentials q which tend to −∞ (or ∞) at infinity, such that 1/q is of bounded variation, have a purely absolutely continuous spectrum covering the whole real line. We show that, for the system on a half-line, there are no local maxima of the spectral density (points of spectral concentration) above some value of the spectral parameter if q satisfies certain additional regularity conditions. These conditions admit thrice-differentiable potentials of power or exponential growth. The eventual sign of the derivative of the spectral density depends on the boundary condition imposed at the regular end-point.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 2005

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