Multiscale cosmology and structure-emerging Dark Energy: A plausibility
  analysis
  Cosmological backreaction suggests a link between structure formation and the
expansion history of the Universe. In order to quantitatively examine this
connection, we dynamically investigate a volume partition of the Universe into
over-- and underdense regions. This allows us to trace structure formation
using the volume fraction of the overdense regions $\lambda_{\CM}$ as its
characterizing parameter. Employing results from cosmological perturbation
theory and extrapolating the leading mode into the nonlinear regime, we
construct a three--parameter model for the effective cosmic expansion history,
involving $\lambda_{\CM_{0}}$, the matter density $\Omega_{m}^{\CD_{0}}$, and
the Hubble rate $H_{\CD_{0}}$ of today's Universe. Taking standard values for
$\Omega_{m}^{\CD_{0}}$ and $H_{\CD_{0}}$ as well as a reasonable value for
$\lambda_{\CM_{0}}$, that we derive from $N$--body simulations, we determine
the corresponding amounts of backreaction and spatial curvature. We find that
the obtained values that are sufficient to generate today's structure also lead
to a $\Lambda$CDM--like behavior of the scale factor, parametrized by the same
parameters $\Omega_{m}^{\CD_{0}}$ and $H_{\CD_{0}}$, but without a cosmological
constant. However, the temporal behavior of $\lambda_{\CM}$ does not faithfully
reproduce the structure formation history. Surprisingly, however, the model
matches with structure formation with the assumption of a low matter content,
$\Omega_{m}^{\CD_{0}}\approx3\%$, a result that hints to a different
interpretation of part of the backreaction effect as kinematical Dark Matter.
(truncated)
