Dark energy versus 
in the growth of matter perturbations
1
Departamento de Física Teórica, Universidad de Zaragoza, 50009 Zaragoza, Spain e-mail: membrado@unizar.es
2
Instituto de Astrofísica de Canarias, 38200 La Laguna, Spain e-mail: jalfonso@ll.iac.es
Received:
24
July
2003
Accepted:
2
June
2004
We explore the possibility of discriminating dark energy models from the study of the growth of matter perturbations. For the sake of simplicity, instead of dealing with a great number of models, we have chosen a simple model of dark energy (
, with 
and 
; px, and 
being pressure and energy density), which is able to reproduce a great number of different behaviours.
A combination of WMAP data with other results have been used to estimate model parameters.
The study has been made for collapsing shells in spherical clusters virialized at redshifts 
, 0.1 and 0.025 with line-of-sight velocity dispersion
and 
.
According to shell velocities, our dark energy models are clearly differentiated from the
model (the greater the 
is, the more differentiated the models are). However, the differences among dark energy models are not so large. From our results, the nearest clusters with large are the idoneous ones to discriminate models. In fact, we think that from observations of caustics in nearby spherical clusters, it would be possible to make an estimation of 
.
Key words: cosmology: theory
© ESO, 2004