526 research outputs found
Cosmological test on viscous bulk models using Hubble Parameter measurements and type Ia Supernovae data
From a phenomenological point of view, we analyze the dynamics of the
Universe at late times by introducing a polynomial and hyperbolic bulk
viscosity into the Einstein field equations respectively. We constrain their
free parameters using the observational Hubble parameter data and the Type Ia
Supernovae dataset to reconstruct the deceleration and the jerk
parameters within the redshift region . At current epochs, we obtain
and for the
polynomial model and
() and
() for the tanh (cosh) model. Furthermore, we explore
the statefinder diagnostic that gives us evident differences with respect to
the concordance model (LCDM). According to our results this kind of models is
not supported by the data over LCDM.Comment: Accepted for publication in EPJ
A hybrid model of viscous and Chaplygin gas to tackle the Universe acceleration
Motivated by two seminal models proposed to explain the Universe
acceleration, this paper is devoted to study a hybrid model which is
constructed through a generalized Chaplygin gas with the addition of a bulk
viscosity. We call the model a Viscous Generalized Chaplygin Gas (VGCG) and its
free parameters are constrained through several cosmological data like the
Observational Hubble Parameter, Type Ia Supernovae, Baryon Acoustic
Oscillations, Strong Lensing Systems, HII Galaxies and using Joint Bayesian
analysis. In addition, we implement a Om-diagnostic to analyze the VGCC
dynamics and its difference with the standard cosmological model. The hybrid
model shows important differences when compared with the standard cosmological
model. Finally, based on our Joint analysis we find that the VGCG could be an
interesting candidate to alleviate the well-known Hubble constant tension.Comment: Accepted for publication in EPJ
An exponential equation of state of dark energy in the light of 2018 CMB Planck data
The dynamics of the Universe is analyzed using an exponential function for
the dark energy equation of state, known as Gong-Zhang parameterization. The
phase space of the free parameters presented in the model is constrained using
Cosmic Microwave Background radiation, Cosmic Chronometers, modulus distance
from Hydrogen II Galaxies, Type Ia Supernovae and measurements from Baryon
Acoustic Oscillations, together with a stronger bound from a Joint analysis.
The cosmological model is confronted with CDM, observing there is a
strong evidence for CDM in the Joint analysis although the exponential
model is preferred when the data are separated. Based on the Joint analysis, a
value of is found for the characteristic
parameter presented in the equation of state. Additionally, the cosmographic
parameters at current times are reported, having , , and a transition
deceleration-acceleration redshift .
Furthermore, the age of the Universe is estimated as Gyrs. Finally, we open a discussion if this model
could alleviate the and tensions.Comment: Accepted in Physics of Dark Univers
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