Issue |
A&A
Volume 443, Number 3, December I 2005
|
|
---|---|---|
Page(s) | 819 - 830 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20053637 | |
Published online | 15 November 2005 |
Cosmological structure formation in a homogeneous dark energy background
1
Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK e-mail: wjp@roe.ac.uk
2
Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth P01 2EG, UK
Received:
15
June
2005
Accepted:
5
August
2005
There is now strong evidence that the current energy density
of the Universe is dominated by dark energy with an equation of state
, which is causing accelerated expansion. The build-up of
structure within such Universes is subject to significant ongoing
study, particularly through the spherical collapse model. This paper
aims to review and consolidate progress for cosmologies in which the
dark energy component remains homogeneous on the scales of the
structures being modelled. The equations presented are designed to
allow for dark energy with a general time-varying equation of state
. In addition to reviewing previous work, a number of new
results are introduced: a new fitting formula for the linear growth
factor in constant w cosmologies is given. A new formalism for
determining the critical density for collapse is presented based on
the initial curvature of the perturbation. The commonly used
approximation to the critical density for collapse based on the linear
growth factor is discussed for a general dark energy equation of
state. Virialisation within such cosmologies is also considered, and
the standard assumption that energy is conserved between turn-around
and virialisation is questioned and limiting possiblities are
presented.
Key words: cosmology: theory / large-scale structure of Universe
© ESO, 2005
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