Apparent Acceleration through Large-scale Inhomogeneities --Post-Friedmannian Effects of Inhomogeneities on the Luminosity Distance--

We re-analyze the observed magnitude-redshift relation of type Ia supernovae (SNe Ia) and examine the possibility that the apparent acceleration of the cosmic expansion is not caused by dark energy but is instead a consequence of the large-scale inhomogeneities in the universe. We propose a method to phenomenologically describe the effects of the large-scale inhomogeneities without relying on the specific toy models of the inhomogeneous universe. This method clearly illustrates how the post-Friedmannian effects of inhomogeneities, i.e. the effects due to the deviation from a perfectly homogeneous and isotropic model, act as an effective cosmological constant in the magnitude-redshift relation of SNe Ia.