The periodic Dirac operator is absolutely continuous

1999 ◽  
Vol 34 (4) ◽  
pp. 377-395 ◽  
Author(s):  
M. Sh. Birman ◽  
T. A. Suslina
Author(s):  
B. J. Harris

SynopsisIn an earlier paper we considered periodic Dirac operators and obtained criteria for them to be self-adjoint and for their spectra to be devoid of eigenvalues of finite multiplicity. The question of the existence of eigenvalues of infinite multiplicity was left open. In this article we obtain further criteria for self-adjointness and show that under these conditions periodic Dirac operators do not possess eigenvalues of infinite multiplicity. We also obtain a spectral gap result.


1997 ◽  
Vol 122 (2) ◽  
pp. 377-384 ◽  
Author(s):  
KARL MICHAEL SCHMIDT

It is shown that the spectrum of a one-dimensional Dirac operator with a potential q tending to infinity at infinity, and such that the positive variation of 1/q is bounded, covers the whole real line and is purely absolutely continuous. An example is given to show that in general, pure absolute continuity is lost if the condition on the positive variation is dropped. The appendix contains a direct proof for the special case of subordinacy theory used.


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