Nabile Boussaid and Sylvain Golenia
Limiting absorption principle for some long range 
perturbations of Dirac systems at threshold energies
(117K, latex)

ABSTRACT.  We establish a limiting absorption principle for some long range 
perturbations of the Dirac systems at threshold energies. We cover 
multi-center interactions with small coupling constants. 
The analysis is reduced to study a family of non-self-adjoint 
operators. The technique is based on a positive commutator theory 
for non self-adjoint operators, which we develop in appendix. We also 
discuss some applications to the dispersive Helmholzt model in the 
quantum regime.