Phenomenological models for unified dark matter with fast transition

Bruni, Marco; Lazkoz, Ruth; Rozas-Fernández, Alberto

doi:10.1093/mnras/stt395

Cited by 22 publications

(21 citation statements)

References 49 publications

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“…A similar feature was also observed in [37] for their power law model of F. We note that this is very similar to other models which introduce a new cosmological fluid with a negative squared sound speed, c 2 s = δP/δρ. We solve the differential equation governing the evolution of Φ [65,66]…”

Section: Iv3 Dynamics Of Linear Perturbations In the Scalar Sectormentioning

confidence: 99%

Cosmological perturbation theory in generalized Einstein-Aether models

2017

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We investigate the evolution of cosmological perturbations in models of dark energy described by a timelike unit normalized vector field specified by a general function F ðKÞ, so-called generalized EinsteinAether models. First we study the background dynamics of such models via a designer approach in an attempt to model this theory as dark energy. We find that only one specific form of this designer approach matches ΛCDM at background order, and we also obtain a differential equation which F ðKÞ must satisfy for general wCDM cosmologies, where CDM refers to cold dark matter. We also present the equations of state for perturbations in generalized Einstein-Aether models, which completely parametrize these models at the level of linear perturbations. A generic feature of modified gravity models is that they introduce new degrees of freedom. By fully eliminating these we are able to express the gauge invariant entropy perturbation and the scalar, vector, and tensor anisotropic stresses in terms of the perturbed fluid variables and metric perturbations only. These can then be used to study the evolution of perturbations in the scalar, vector, and tensor sectors, and we use these to evolve the Newtonian gravitational potentials.

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Section: Iv3 Dynamics Of Linear Perturbations In the Scalar Sectormentioning

confidence: 99%

Cosmological perturbation theory in generalized Einstein-Aether models

2017

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“…Being more specific about the sources, we need to clarify the role and form of our proposed UDE/M fluid: we want a UDE/M fluid which exhibits a fast transition from the pure dark matter stage to a scenario that resembles a ΛCDM set-up. From [27], we borrow the analytical form…”

Section: Ude/m Modelsmentioning

confidence: 99%

“…A simple model, gentle on computations, must be one whose most important variables required for the numerical calculations can be expressed analytically. Thus, instead of implementing the UDE/M model in the equation of state w UDE/M , as in [25], we believe a more convenient way to proceed analytically is to prescribe the evolution of the UDE/M energy density at the level of the Hubble factor itself [27]. Here we present (in section II) two parametrizations for these UDE/M set-ups with fast transition.…”

Section: Introductionmentioning

confidence: 99%

Cosmological constraints on fast transition unified dark energy and dark matter models

2016

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We explore the observational adequacy of a class of Unified Dark Energy/Matter (UDE/M) models with a fast transition. Our constraints are set using a combination of geometric probes, some low redshift ones, and some high redshift ones (CMB related included). The transition is phenomenologically modeled by two different transition functions corresponding to a fast and to an ultra-fast transition respectively. We find that the key parameters governing the transition can be well constrained, and from the statistical point of view it follows that the models cannot be discarded when compared to LCDM. We find the intriguing result that standard/input parameters such as Ωm and Ω b are far better constrained than in LCDM, and this is the case for the derived/output parameter measuring the deceleration value at present, q0.

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“…Such models have been explored in the literature under the name "quartessence" models -see e.g. [28][29][30][31][32][33][34] and references therein. In particular, the authors in Ref.…”

Section: Introductionmentioning

confidence: 99%

Analytic study of cosmological perturbations in a unified model of dark matter and dark energy with a sharp transition

Cuzinatto

Medeiros

Morais

et al. 2018

Astroparticle Physics

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We study cosmological perturbations in a model of unified dark matter and dark energy with a sharp transition in the late-time universe. The dark sector is described by a dark fluid which evolves from an early stage at redshifts z > zC when it behaves as cold dark matter (CDM) to a late time dark energy (DE) phase (z < zC ) when the equation of state parameter is w = −1 + , with a constant which must be in the range 0 < < 2/3. We show that fluctuations in the dark energy phase suffer from an exponential instability, the mode functions growing both as a function of comoving momentum k and of conformal time η. In order that this exponential instability does not lead to distortions of the energy density power spectrum on scales for which we have good observational results, the redshift zC of transition between the two phases is constrained to be so close to zero that the model is unable to explain the supernova data.

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Phenomenological models for unified dark matter with fast transition

Cited by 22 publications

References 49 publications

Cosmological perturbation theory in generalized Einstein-Aether models

Cosmological perturbation theory in generalized Einstein-Aether models

Cosmological constraints on fast transition unified dark energy and dark matter models

Analytic study of cosmological perturbations in a unified model of dark matter and dark energy with a sharp transition

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