Linear perturbations in a universe with a cosmological constant

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dc.creatorVale, Antonio
dc.creatorLemos, Jose' P. S.
dc.date2001-01-28
dc.date2001-10-14
dc.date.accessioned2026-07-07T10:51:18Z
dc.date.available2026-07-07T10:51:18Z
dc.descriptionThere are now evidences that the cosmological constant $Λ$ has a non-zero positive value. Alternative scenarios to a pure cosmological constant model are provided by quintessence, an effective negative pressure fluid permeating the universe. Recent results indicate that the energy density $ρ$ and the pressure $p$ of this fluid are constrained by $-ρ\leq p \buildrel<\over\sim-0.6 ρ$. Since $p=-ρ$ is equivalent to the pure cosmological constant model, it is appropriate to analyze this particular, but important, case further. We study the linear theory of perturbations in a Friedmann-Robertson-Walker universe with a cosmological constant. We obtain the equations for the evolution of the perturbations in the fully relativistic case, for which we analyze the single-fluid and the two-fluid cases. We obtain solutions to these equations in appropriate limits. We also study the Newtonian approximation. We find that for a positive cosmological constant universe (i) the perturbations will grow slower in the relativistic regime for a two-fluid composed of dark matter and radiation, and (ii) in the Newtonian regime, the perturbations stop growing.
dc.description23 pages, 1 figure, latex; references added, extended introduction
dc.identifierhttps://arxiv.org/abs/astro-ph/0101500
dc.identifierhttp://arxiv.org/abs/astro-ph/0101500
dc.identifierMon.Not.Roy.Astron.Soc.325:1197-1204,2001
dc.identifierdoi:10.1046/j.1365-8711.2001.04542.x
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/184774
dc.subjectAstrophysics
dc.subjectGeneral Relativity and Quantum Cosmology
dc.titleLinear perturbations in a universe with a cosmological constant
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