  We report on the direct numerical measurements of the conductivity of
graphene monolayer. Our numerical simulations are performed in the effective
lattice field theory with noncompact 3 + 1-dimensional Abelian lattice gauge
fields and 2 + 1-dimensional staggered lattice fermions. The conductivity is
obtained from the Green-Kubo relations using the Maximum Entropy Method. We
find that in a phase with spontaneously broken sublattice symmetry the
conductivity rapidly decreases. For the largest value of the coupling constant
used in our simulations g = 4.5, the DC conductivity is less than the DC
conductivity in the weak-coupling phase (at g < 3.5) by at least three orders
of magnitude.
