The isotropic and homogeneous FLRW cosmological model
has been so successful in describing the observable Universe
that it is commonly referred to as the ``standard model''.
Furthermore, and to its credit, the model is relatively simple
so that it allows for calculations and predictions
to be made of the very early Universe, including
primordial nucleosynthesis at 
seconds
after the Big Bang, and even
particle interactions approaching the Planck
scale at 
seconds.
At present, observational support for the standard model includes:
- the expansion of the Universe
as verified by the redshifts
in galaxy spectra and quantified by measurements of
the Hubble constant
; - the deceleration parameter
observed in
distant galaxy spectra (although uncertainties about
galactic evolution, intrinsic luminosities,
and standard candles prevent an accurate estimate);
- the large scale isotropy and homogeneity of the Universe
based on temperature anisotropy measurements of the
microwave background radiation and
peculiar velocity fields of galaxies
(although the light distribution from bright galaxies is
somewhat contradictory);
- the age of the Universe
which yields roughly consistent estimates between the look-back
time to the Big Bang in the FLRW model and observed data such
as the oldest stars, radioactive elements, and cooling of
white dwarf stars;
- the cosmic microwave background radiation
suggests that the Universe began from a hot Big Bang
and the data is consistent with a mostly isotropic model and a black
body at temperature 2.7 K;
- the abundance of light elements
such as
H, 
He, 
He and 
Li, as predicted from
the FLRW model, is consistent with observations and
provides a bound on the baryon density and baryon-to-photon
ratio; - the present mass density,
as determined from measurements of
luminous matter and galactic rotation curves,
can be accounted for by the FLRW model with a single density
parameter (
) to specify the metric topology; - the distribution of galaxies and larger scale structures
can be reproduced by numerical simulations
in the context of inhomogeneous perturbations of the FLRW models.
Because of these successes, most work in the field
of physical cosmology (see § 4)
has utilized the standard model as the background spacetime
in which the large scale structure evolves, with the
ambition to further constrain parameters
and structure formation scenarios
through numerical simulations.
The reader is referred to [84
]
for a more in-depth review of the standard model,
and to [102, 119]
for a summary of observed cosmological
parameter constraints and best fit ``concordance'' models.
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Computational Cosmology: from the Early Universe to the Large Scale Structure
Peter Anninos
http://www.livingreviews.org/lrr-2001-2
© Max-Planck-Gesellschaft. ISSN 1433-8351
Problems/Comments to livrev@aei-potsdam.mpg.de
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