Cosmic Acceleration as an Optical Illusion
  We consider light propagation in an inhomogeneous irrotational dust universe
with vanishing cosmological constant, with initial conditions as in standard
linear perturbation theory. A non-perturbative approach to the dynamics of such
a universe is combined with a distance formula based on the Sachs optical
equations. Then a numerical study implies a redshift-distance relation that
roughly agrees with observations. Interpreted in the standard homogeneous
setup, our results would appear to imply the currently accepted values for the
Hubble rate and the deceleration parameter; furthermore there is consistency
with density perturbations at last scattering. The determination of these three
quantities relies only on a single parameter related to a cutoff scale.
Discrepancies with the existing literature are related to subtleties of higher
order perturbation theory which make both the reliability of the present
approach and the magnitude of perturbative effects beyond second order hard to
assess.
