  We study the influence of lattice deformations on the optical conductivity of
a two-dimensional electron gas. Lattice deformations are taken into account by
introducing a non-abelian gauge field into the Eucledian action of
two-dimensional Dirac electrons. This is in analogy to the introduction of the
gravitation in the four-dimensional quantum field theory. We examine the effect
of these deformations on the averaged optical conductivity. Within the
perturbative theory up to second order we show that corrections of the
conductivity due to the deformations cancel each other exactly. We argue that
these corrections vanish to any order in perturbative expansion.
