منابع مشابه
Constraints on alternative models to dark energy
The recent observations of type Ia supernova strongly support that the universe is accelerating now and decelerated in the recent past. This may be the evidence of the breakdown of the standard Friedmann equation. We consider a general modified Friedmann equation. Three different models are analyzed in detail. The current supernova data and the Wilkinson microwave anisotropy probe data are used...
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We explore the possibility that the present stage of accelerated expansion of the universe is due to the presence of a cosmic vector field. We show that vector theories allow for the generation of an accelerated phase without the introduction of potential terms or unnatural scales in the Lagrangian. We propose a particular model with the same number of parameters as ΛCDM and excellent fits to S...
متن کاملSupernova constraints on alternative models to dark energy
The recent observations of type Ia supernovae suggest that the universe is accelerating now and decelerated in the recent past. This may be the evidence of the breakdown of the standard Friedmann equation. The Friedmann equation H ∼ ρ is modified to be a general form H = g(ρ). Three models with particular form of g(ρ) are considered in detail. The supernova data published by Tonry et al. (2003)...
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We explore the dynamics of dark energy models based on a Dirac-Born-Infeld (DBI) tachyonic action, studying a range of potentials. We numerically investigate the existence of tracking behavior and determine the present-day value of the equation of state parameter and its running, which are compared with observational bounds. We find that tachyon models have quite similar phenomenology to canoni...
متن کاملCosmological Perturbations in Phantom Dark Energy Models
The ΛCDM paradigm, characterised by a constant equation of state w = −1 for dark energy, is the model that better fits observations. However, the same observations strongly support the possibility of a dark energy content where the corresponding equation of state is close to but slightly smaller than −1. In this regard, we focus on three different models where the dark energy content is describ...
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ژورنال
عنوان ژورنال: Advances in Space Research
سال: 2018
ISSN: 0273-1177
DOI: 10.1016/j.asr.2017.08.006