  It has been observed more than 25 years ago that sigma model perturbation
theory suffers from strongly RG-relevant high-gradient operators. The
phenomenon was first seen in 1-loop calculations for the O(N) vector model and
it is known to persist at least to two loops. More recently, Ryu et al.
suggested that a certain deformation of the psl(N|N) WZNW-model at level k = 1,
or equivalently the psl(N|N) Gross-Neveu model, could be free of RG-relevant
high-gradient operators and they tested their suggestion to leading order in
perturbation theory. In this note we establish the absence of strongly
RG-relevant high-gradient operators in the psl(2|2) Gross-Neveu model to all
loops. In addition, we determine the spectrum for a large subsector of the
model at infinite coupling and observe that all scaling weights become
half-integer. Evidence for a conjectured relation with the CP^1|2 sigma model
is not found.

High Energy Physics - Theory