Papers › Probing a Steep EoS for Dark Energy with latest observations
Probing a Steep EoS for Dark Energy with latest observations
Mariana Jaber, Axel de la Macorra
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We present a parametrization for the Dark Energy Equation of State "EoS" which has a rich structure, performing a transition at pivotal redshift z_T between the present day value w₀ to an early time wᵢ=wₐ+w₀≡w(z≫0) with a steepness given in terms of q parameter. The proposed parametrization is w=w₀+wₐ(z/z_T)^q/(1+(z/z_T))^q, with w₀, wᵢ, $q $ and z_T constant parameters. It reduces to the widely used EoS w=w₀+wₐ(1-a) for z_T=q=1. This transition is motivated by scalar field dynamics such as for example quintessence models. We study if a late time transition is favored by BAO measurements combined with local determination of H₀ and information from the CMB. According to our results, an EoS with a present value of w₀ = -0.92 and a high redshift value wᵢ =-0.99, featuring a transition at z_T = 0.28 with an exponent q = 9.97 was favored by data coming from local dynamics of the Universe (BAO combined with H₀ determination). We find that a dynamical DE model allows to simultaneously fit H₀ from local determinations and Planck CMB measurements, alleviating the tension obtained in a ΛCDM model. Additionally to this analysis we solved numerically the evolution of matter over-densities in the presence of dark energy both at background level and when its perturbations were considered. We show that the presence of a steep transition in the DE EoS gets imprinted into the evolution of matter overdensities and that the addition of an effective sound speed term does not erase such feature.
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