Below is the ascii version of the abstract for 99-29. The html version should be ready soon.

V. Georgescu, M. Mantoiu
On the Spectral Theory of Dirac Type Hamiltonians
(616K, Postscript)

ABSTRACT.  We introduce a class of matrix valued pseudo-differential operators that admit scalar 
locally conjugate operators (in the sense of E. Mourre) and we give a general method 
for studying singular perturbations of such operators. 
In particular, we develop the spectral and scattering theory for a class of hamiltonians 
which contains the Dirac operators with arbitrary Coulomb singularities.