The Dirac Operator; From Numerics to the Theory of G-convergence
Licentiate thesis, 2010
We consider two main issues concerning the Dirac operator, the first is widely
known as the appearance of spurious eigenvalues within the spectrum. The second
is the study of the asymptotic behavior of the eigenvalues for a family of
Dirac operators with oscillatory potential added to the Coulomb-Dirac Hamiltonian.
In the first problem a stable Finite element scheme is used to treat the problem
of spuriousity of the radial Dirac operator with a Coulomb potential. The numerical
accuracy depends strongly on the derivation of a fine-intrinsic stability
In the second problem we consider the Coulomb-Dirac operator with addition
to an abstract oscillating potential. Using the spectral measure of operators
we project into the positive part of the perturbed Hamiltonian. By using G-convergence
theory of positive self-adjoint operators in Hilbert spaces and ¡-
convergence of the associated quadratic functionals we prove G-compactness
for a family of positive Dirac operators under certain assumptions on the potentials.