The Discrete Spectra of the Dirac and Pauli Operators
The aim of the present article is the investigation of the spectra of the Dirac and Pauli operators by operator-theoretic methods. This investigation is based on the estimation of the quadratic forms of the above operators by means of the quadratic forms of operators with well-known spectra. We may count the Schroedinger operator among the latter. Estimates of this type extended to both sides allow us, in some cases, to establish the criteria for the total multiplicity of the spectrum of the perturbed operator to be finite or infinite in that part of the axis which min the case of the unperturbed operator is a gap (i.e., free from the spectrum). Qualitative conclusions on the character of the spectrum and quantitative estimates of the total multiplicity of the spectrum follow from the well-known properties of the Schroedinger operator. In some cases, these conclusions refer to a family of operators obtained through the introduction of a parameter h which plays the part of Planck’s constant in quantum mechanics. Skachek  has recently obtained the lower bound to the number of eigenvalues of the Dirac operator. By contrast with the results of , our estimates do not contain terms involving the derivative of the potential. Some results concerning the spectrum of the Pauli operator have been obtained by Glazman .
KeywordsDirac Operator Discrete Spectrum Linear Manifold Pauli Operator Finite Function
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