Cosmic Acceleration and a New Concordance from Causal Backreaction
  A phenomenological formalism is presented in which the apparent acceleration
of the universe is generated by large-scale structure formation, thus
eliminating the magnitude and coincidence fine-tuning problems of the
Cosmological Constant in the Concordance Model, as well as potential
instability issues with dynamical Dark Energy. The observed acceleration
results from the combined effect of innumerable local perturbations due to
individually virializing systems, overlapping together in a
smoothly-inhomogeneous adjustment of the FRW metric, in a process governed by
the causal flow of inhomogeneity information outward from each clumped system.
After explaining why arguments from the literature claiming to place
restrictive limits upon backreaction are not applicable in a physically
realistic cosmological analysis, we present a selection of simply-parameterized
models which are capable of fitting the luminosity distance data from Type Ia
supernovae essentially as well as the best-fit flat $\Lambda$CDM model, without
resort to Dark Energy, any modification to gravity, or a local void.
Simultaneously, these models can reproduce measured cosmological parameters
such as the age of the universe, the matter density required for spatial
flatness, the present-day deceleration parameter, and the angular scale of the
Cosmic Microwave Background to within a reasonable proximity of their
Concordance values. A potential observational signature for distinguishing this
cosmological formalism from $\Lambda$CDM may be a cosmic jerk parameter
significantly in excess of unity.
