Bibcode
Aguerri, J. A. L.; Membrado, M.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 302, Issue 4, pp. 625-631.
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2
1999
Citations
1
Refereed citations
1
Description
We investigate the cosmology of x-matter with pressure, px,
and density, ρx, related by
px=w0ργx(w0<0γ
>0). For γ >1, this x-matter behaves like a cosmological
constant when a<< a0 (a being the scalefactor and
a0 the scalefactor at present) and like matter for a γ
a0; for γ <1, the behaviour is the opposite; for
γ =1, the x-matter density varies as
a-3(1+w0). Models of x-matter with γ >1
reach, at all times, densities lower than do models with γ <= 1
for equal present x-matter density, so the former have less effect on
the formation of structures in the Universe. Allowed values for the free
parameters of these cosmological models are estimated by imposing two
observational constraints which originate from the age problem of the
Universe and from the luminosity-distance relation for Type Ia
supernovae at z=0.4.