Asao Arai
Ground State
of the Massless Nelson Model Without
Infrared Cutoff in a Non-Fock Representation
(47K, LaTex)

ABSTRACT.  We consider a model of quantum particles
coupled to a  massless  quantum scalar
field, called the massless Nelson model,
{\it in a non-Fock representation} of the
time-zero fields which satisfy the canonical commutation
relations.
We show that the model has
a ground  state
for {\it all} values of the coupling
constant {\it even in the case where
no infrared cutoff
is made}. The non-Fock representation used
is inequivalent to the Fock one
if no infrared cutoff is made.