Dense point spectrum for the one-dimensional Dirac operator with an electrostatic potential

1996 ◽  
Vol 126 (5) ◽  
pp. 1087-1096 ◽  
Author(s):  
Karl Michael Schmidt

For the one-dimensional Dirac operator, examples of electrostatic potentials with decay behaviour arbitrarily close to Coulomb decay are constructed for which the operator has a prescribed set of eigenvalues dense in the whole or part of its essential spectrum. A simple proof that the essential spectrum of one-dimensional Dirac operators with electrostatic potentials is never empty is given in the appendix.

2010 ◽  
Vol 82 (1) ◽  
pp. 617-620 ◽  
Author(s):  
V. M. Kurbanov ◽  
A. I. Ismailova

1994 ◽  
Vol 09 (07) ◽  
pp. 623-630
Author(s):  
MINOS AXENIDES ◽  
HOLGER BECH NIELSEN ◽  
ANDREI JOHANSEN

We present a simple exactly solvable quantum mechanical example of the global anomaly in an O(3) model with an odd number of fermionic triplets coupled to a gauge field on a circle. Because the fundamental group is non-trivial, π1(O(3))=Z2, fermionic level crossing—circling occurs in the eigenvalue spectrum of the one-dimensional Dirac operator under continuous external field transformations. They are shown to be related to the presence of an odd number of normalizable zero modes in the spectrum of an appropriate two-dimensional Dirac operator. We argue that fermionic degrees of freedom in the presence of an infinitely large external field violate perturbative decoupling.


Geophysics ◽  
1975 ◽  
Vol 40 (2) ◽  
pp. 325-330 ◽  
Author(s):  
D. Loewenthal

A simple proof that the phase of the one‐ dimensional magnetotelluric modified impedance lies between −π/4 and π/4 is given. The proof is based upon a rational polynomial representation of the impedance. The formalism from which the rational representation is obtained is outlined. An adjoint model is defined and it is shown to be pertinent for the proof. A numerical example is given.


Geophysics ◽  
1975 ◽  
Vol 40 (6) ◽  
pp. 1076-1076
Author(s):  
Donald H. Eckhard

In his paper, Loewenthal presents what he calls a “simple proof” that the phase of the one‐dimensional magnetotelluric modified impedance lies between −π/4 and π/4. A much simpler proof exists (Eckhardt, 1968). My proof is buried as a rather minor feature of an obscure (alas) paper, and some of its sign conventions differ from standard, so I believe it appropriate to restate the proof here.


2016 ◽  
Vol 94 (1) ◽  
pp. 401-405
Author(s):  
Z. S. Aliev ◽  
Kh. Sh. Rzaeva

2005 ◽  
Vol 46 (7) ◽  
pp. 072105 ◽  
Author(s):  
César R. de Oliveira ◽  
Roberto A. Prado

2020 ◽  
Vol 139 (12) ◽  
Author(s):  
Jacek Karwowski ◽  
Artur Ishkhanyan ◽  
Andrzej Poszwa

AbstractThe properties of the eigenvalue problem of the one-dimensional Dirac operator are discussed in terms of the mutual relations between vector, scalar and pseudo-scalar contributions to the potential. Relations to the exact solubility are analyzed.


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