Vladimir Georgescu
Spectral Analysis of Quantum Field Models with a Particle 
Number Cutoff
(171K, Postscript)

ABSTRACT.  We determine the essential spectrum and prove the absence of singular 
continuous spectrum for a class of boson quantum field models with 
cutoffs. Our main purpose, however, is to show the power of an 
algebraic technique based on the study of the $C^*$-algebra generated 
by the operators which are natural candidates as hamiltonians of the 
system in a given physical situation.