C. Tix
Strict positivity of a relativistic Hamiltonian due to Brown and
Ravenhall
(24K, LaTeX2e)

ABSTRACT.  We prove that the spectrum of a suitably projected Dirac
operator - sometimes called no-pair operator -- introduced by Brown
and Ravenhall is bounded from below by some positive constant when the
nuclear charge is below some critical charge. This bound improves a
result obtained recently by Evans et al and disproves a conjecture
made by Hardekopf and Sucher.