Are dark energy models with variable EoS parameter<i>w</i>compatible with the late inhomogeneous Universe?

Akarsu, Özgür; Bouhmadi-López, Mariam; Brilenkov, Maxim; Brilenkov, Ruslan; Eingorn, Maxim; Zhuk, Alexander

doi:10.1088/1475-7516/2015/07/038

Cited by 12 publications

(30 citation statements)

References 25 publications

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“…We note that coupled states of perfect fluids were investigated in the case of a perfect fluid with a constant equation of state parameter [25] and for the following cosmological scenarios and constituents of the Universe: quark-gluon nuggets [27], the CPL model [28], Chaplygin gas [29], nonlinear f (R) gravity [30], as well as the models with a scalar field [31,32] and dark sector interactions [33,34].…”

Section: Equations For Gravitational Potential φmentioning

confidence: 99%

Scalar and vector perturbations in a universe with discrete and continuous matter sources

Eingorn

Kiefer

Zhuk

2016

J. Cosmol. Astropart. Phys.

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Abstract. We study a universe filled with dust-like matter in the form of discrete inhomogeneities (e.g., galaxies and their groups and clusters) and two sets of perfect fluids with linear and nonlinear equations of state, respectively. The background spacetime geometry is defined by the FLRW metric. In the weak gravitational field limit, we develop the first-order scalar and vector cosmological perturbation theory. Our approach works at all cosmological scales (i.e. sub-horizon and super-horizon ones) and incorporates linear and nonlinear effects with respect to energy density fluctuations. We demonstrate that the scalar perturbation (i.e. the gravitational potential) as well as the vector perturbation can be split into individual contributions from each matter source. Each of these contributions satisfies its own equation. The velocity-independent parts of the individual gravitational potentials are characterized by a finite time-dependent Yukawa interaction range being the same for each individual contribution. We also obtain the exact form of the gravitational potential and vector perturbation related to the discrete matter sources. The self-consistency of our approach is thoroughly checked. The derived equations can form the theoretical basis for numerical simulations for a wide class of cosmological models.

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Section: Equations For Gravitational Potential φmentioning

confidence: 99%

Scalar and vector perturbations in a universe with discrete and continuous matter sources

Eingorn

Kiefer

Zhuk

2016

J. Cosmol. Astropart. Phys.

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“…Linear parametrizations of the dark energy EOS (the CPL EOS is linear in the scale factor a) are not compatible with the theory of scalar perturbations in the late Universe. Therefore these EOS are not the fundamental and can only be used to approximate the real EOS Akarsu et al (2015). In our approach, this model is only used to investigate whether the EOS is constant, independently of any assumption on the nature of the DE: according to this point of view, even the small number of parameters of the CPL model is not as important as this independence (in some scalar field models of dark energy, the so-called quintessence, first introduced in Peebles & Ratra 1988a;Ratra & Peebles 1988b, the scalar field has one free parameter less than CPL).…”

Section: Introductionmentioning

confidence: 99%

Cosmology with gamma-ray bursts

Demiański

Piedipalumbo

Sawant

et al. 2017

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Context. Explaining the accelerated expansion of the Universe is one of the fundamental challenges in physics today. Cosmography provides information about the evolution of the universe derived from measured distances, assuming only that the space time geometry is described by the Friedman-Lemaitre-Robertson-Walker metric, and adopting an approach that effectively uses only Taylor expansions of basic observables. Aims. We perform a high-redshift analysis to constrain the cosmographic expansion up to the fifth order. It is based on the Union2 type Ia supernovae data set, the gamma-ray burst Hubble diagram, a data set of 28 independent measurements of the Hubble parameter, baryon acoustic oscillations measurements from galaxy clustering and the Lyman-α forest in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), and some Gaussian priors on h and Ω M . Methods. We performed a statistical analysis and explored the probability distributions of the cosmographic parameters. By building up their regions of confidence, we maximized our likelihood function using the Markov chain Monte Carlo method. Results. Our high-redshift analysis confirms that the expansion of the Universe currently accelerates; the estimation of the jerk parameter indicates a possible deviation from the standard ΛCDM cosmological model. Moreover, we investigate implications of our results for the reconstruction of the dark energy equation of state (EOS) by comparing the standard technique of cosmography with an alternative approach based on generalized Padé approximations of the same observables. Because these expansions converge better, is possible to improve the constraints on the cosmographic parameters and also on the dark matter EOS. Conclusions. The estimation of the jerk and the DE parameters indicates at 1σ a possible deviation from the ΛCDM cosmological model.

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“…where we also took into account that δp rad = (1/3)δε rad . From this EoS and within the mechanical approach, where the peculiar velocities are assumed to be non-relativistic, we can easily get that δε rad ∼ 1/a 4 (we refer the reader to the appendix of [37] for a derivation of this result). The important point is that, according to Eq.…”

Section: )mentioning

confidence: 97%

“…Therefore, the peculiar velocities of these fluctuations are also non-relativistic, and in the system of equations for the scalar perturbations we can drop the terms containing the peculiar velocities as compared with their energy density and pressure fluctuations. Then, the gravitational potential Φ takes the form [27,28,[35][36][37][38] :…”

Section: (219)mentioning

confidence: 99%

“…The mechanical approach was applied to a number of DE models to study their compatibility with the theory of scalar perturbations. For example, we considered a perfect fluid with a constant equation of state parameter [35], the model with quark-gluon nuggets [36], the CPL model [37], the Chaplygin gas model [38], the non-linear f (R) model [39] and the model with a scalar field [40]. One of the main features of all these models is that perfect fluids (as well as scalar field) are considered in a very specific "coupled" form [41].…”

Section: Introductionmentioning

confidence: 99%

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The late Universe with non-linear interaction in the dark sector: The coincidence problem

Bouhmadi-López

Morais

Zhuk

2016

Physics of the Dark Universe

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Abstract. We study the Universe at the late stage of its evolution and deep inside the cell of uniformity. At such a scale the Universe is highly inhomogeneous and filled with discretely distributed inhomogeneities in the form of galaxies and groups of galaxies. As a matter source, we consider dark matter (DM) and dark energy (DE) with a non-linear interaction Q = 3Hγε DE ε DM /(ε DE + ε DM ), where γ is a constant. We assume that DM is pressureless and DE has a constant equation of state parameter w. In the considered model, the energy densities of the dark sector components present a scaling behaviour with ε DM /ε DE ∼ (a 0 /a) −3(w+γ) . We investigate the possibility that the perturbations of DM and DE, which are interacting among themselves, could be coupled to the galaxies with the former being concentrated around them. To carry our analysis, we consider the theory of scalar perturbations (within the mechanical approach), and obtain the sets of parameters (w, γ) which do not contradict it. We conclude that two sets: (w = −2/3, γ = 1/3) and (w = −1, γ = 1/3) are of special interest. First, the energy densities of DM and DE on these cases are concentrated around galaxies confirming that they are coupled fluids. Second, we show that for both of them, the coincidence problem is less severe than in the standard ΛCDM. Third, the set (w = −1, γ = 1/3) is within the observational constraints. Finally, we also obtain an expression for the gravitational potential in the considered model.

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Are dark energy models with variable EoS parameterwcompatible with the late inhomogeneous Universe?

Cited by 12 publications

References 25 publications

Scalar and vector perturbations in a universe with discrete and continuous matter sources

Scalar and vector perturbations in a universe with discrete and continuous matter sources

Cosmology with gamma-ray bursts

The late Universe with non-linear interaction in the dark sector: The coincidence problem

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