$Λα$DM: Observational constraints on unified dark matter with constant speed of sound
| dc.creator | Balbi, Amedeo | |
| dc.creator | Bruni, Marco | |
| dc.creator | Quercellini, Claudia | |
| dc.date | 2007-02-15 | |
| dc.date | 2007-11-12 | |
| dc.date.accessioned | 2026-07-07T11:00:52Z | |
| dc.date.available | 2026-07-07T11:00:52Z | |
| dc.description | We consider the hypothesis that dark energy and dark matter are the two faces of a single dark component, a unified dark matter (UDM) that we assume can be modeled by the affine equation of state (EoS) $P= p_0 +αρ$, resulting in an {\it effective cosmological constant} $ρ_Λ=-p_0/(1+α)$. The affine EoS arises from the simple assumption that the speed of sound is constant; it may be seen as an approximation to an unknown barotropic EoS $P=P(ρ)$, and may as well represent the tracking solution for the dynamics of a scalar field with appropriate potential. Furthermore, in principle the affine EoS allows the UDM to be phantom. We constrain the parameters of the model, $α$ and $Ω_Λ$, using data from a suite of different cosmological observations, and perform a comparison with the standard $Λ$CDM model, containing both cold dark matter and a cosmological constant. First considering a flat cosmology, we find that the UDM model with affine EoS fits the joint observations very well, better than $Λ$CDM, with best fit values $α=0.01 \pm 0.02$ and $Ω_Λ=0.70 \pm 0.04$ (95% confidence intervals). The standard model (best fit $Ω_Λ=0.71\pm 0.04$), having one less parameter, is preferred by a Bayesian model comparison. However, the affine EoS is at least as good as the standard model if a flat curvature is not assumed as a prior for $Λ$CDM. For the latter, the best fit values are $Ω_K=-0.02^{+0.01}_{-0.02} $ and $Ω_Λ=0.71 \pm 0.04$, i.e. a closed model is preferred. A phantom UDM with affine EoS is ruled out well beyond $3σ$. | |
| dc.description | 7 pages, 4 figures. Matching version published on PRD | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0702423 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0702423 | |
| dc.identifier | Phys.Rev.D76:103519,2007 | |
| dc.identifier | doi:10.1103/PhysRevD.76.103519 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/187791 | |
| dc.subject | Astrophysics | |
| dc.subject | High Energy Physics - Phenomenology | |
| dc.subject | High Energy Physics - Theory | |
| dc.title | $Λα$DM: Observational constraints on unified dark matter with constant speed of sound | |
| dc.type | text |