  A 2+1 dimensional fermion field theory is proposed as a model for the
low-energy electronic excitations in monolayer graphene. The model consists of
N=2 four-component Dirac fermions moving in the plane and interacting via a
contact interaction between charge densities. For strong couplings there is a
continuous transition to a Mott insulting phase. We present results of an
extensive numerical study of the model's critical region, including the order
parameter, its associated susceptibility, and for the first time the
quasiparticle propagator. The data enables an extraction of the critical
exponents at the transition, including the dynamical critical exponent, which
are hypothesised to be universal features of a quantum critical point. The
relation of our model with others in the literature is discussed, along with
the implications for physical graphene following from our value of the critical
coupling.
