Weak cosmic growth in coupled dark energy with a Lagrangian formulation

Kase, Ryotaro; Tsujikawa, Shinji

doi:10.1016/j.physletb.2020.135400

Cited by 32 publications

(30 citation statements)

References 98 publications

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“…For a scalar field φ coupled to the CDM four-velocity u µ c weighed by a scalar quantity Z = u µ c ∂ µ φ [58][59][60][61][62][63][64][65][66][67][68], the interacting Lagrangian like f ∝ Z 2 suppresses the growth of matter perturbations through the momentum exchange between φ and CDM. There are also interacting models based on vector-tensor theories in which the vector field A µ coupled to the CDM four-velocity of the form u µ c A µ leads to weak gravitational couplings for linear cosmological perturbations [69].…”

Section: Introductionmentioning

confidence: 99%

Probing elastic interactions in the dark sector and the role of S8

et al. 2021

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We place observational constraints on two models within a class of scenarios featuring an elastic interaction between dark energy and dark matter that only produces momentum exchange up to first order in cosmological perturbations. The first one corresponds to a perfect-fluid model of the dark components with an explicit interacting Lagrangian, where dark energy acts as a dark radiation at early times and behaves as a cosmological constant at late times. The second one is a dynamical dark energy model with a dark radiation component, where the momentum exchange covariantly modifies the conservation equations in the dark sector. Using Cosmic Microwave Background (CMB), Baryon Acoustic Oscillations (BAO), and Supernovae type Ia (SnIa) data, we show that the Hubble tension can be alleviated due to the additional radiation, while the σ8 tension present in the Λ-Cold-Dark-Matter model can be eased by the weaker galaxy clustering that occurs in these interacting models. Furthermore, we show that, while CMB+BAO+SnIa data put only upper bounds on the coupling strength, adding low-redshift data in the form of a constraint on the parameter S8 strongly favours nonvanishing values of the interaction parameters. Our findings are in line with other results in the literature that could signal a universal trend of the momentum exchange among the dark sector.

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Section: Introductionmentioning

confidence: 99%

Probing elastic interactions in the dark sector and the role of S8

et al. 2021

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“…Such scenarios are particularly useful for providing plausible resolutions to the issue of cosmic coincidence which one usually encounters in scalar field DE models and in the concordant ΛCDM model. One resolution of course comes from the consideration of plausible contact interaction(s) between a scalar field induced DE component and the matter field(s) [1,3,, which the scalar-tensor formulations naturally lead to, under conformal transformations [48][49][50][51][52][53][54][55][56][57]. A DE-matter (DEM) interaction makes the background matter density ρ (m) (z) drifting from its usual (dust-like) evolution with redshift z, thereby affecting the drag force on the matter perturbations.…”

Section: Introductionmentioning

confidence: 99%

Growth of Matter Perturbations in an Interacting Dark Energy Scenario Emerging from Metric-Scalar-Torsion Couplings

Sharma

Sur

2021

The 1st Electronic Conference on Universe

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We study the growth of linear matter density perturbations in a modified gravity approach of scalar field couplings with metric and torsion. In the equivalent scalar-tensor formulation, the matter fields in the Einstein frame interact as usual with an effective dark energy component, whose dynamics is presumably governed by a scalar field that sources a torsion mode. As a consequence, the matter density ceases to be self-conserved, thereby making an impact not only on the background cosmological evolution but also on the perturbative spectrum of the local inhomogeneities. In order to estimate the effect on the growth of the linear matter perturbations, with the least possible alteration of the standard parametric form of the growth factor, we resort to a suitable Taylor expansion of the corresponding exponent, known as the growth index, about the value of the cosmic scale factor at the present epoch. In particular, we obtain an appropriate fitting formula for the growth index in terms of the coupling function and the matter density parameter. While the overall parametric formulation of the growth factor is found to fit well with the latest redshift-space-distortion (RSD) and the observational Hubble (OH) data at low redshifts, the fitting formula enables us to constrain the growth index to well within the concordant cosmological limits, thus ensuring the viability of the formalism.

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“…Models that involve momentum-only interactions can circumvent many of these problems. These models leave the background evolution of the Universe unchanged, only affecting the perturbations [17,[29][30][31][32][33][34]. This allows them to fit the CMB data very well, and to alleviate the σ 8 tension [19,35,36].…”

Section: Introductionmentioning

confidence: 99%

Momentum transfer models of interacting dark energy

Linton,

Crittenden,

Pourtsidou

2021

Preprint

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We consider two models of interacting dark energy, both of which interact only through momentum exchange. One is a phenomenological one-parameter extension to wCDM, and the other is a coupled quintessence model described by a Lagrangian formalism. Using a variety of high and low redshift data sets, we perform a global fitting of cosmological parameters and compare to ΛCDM, uncoupled quintessence, and wCDM. We find that the models are competitive with ΛCDM, even obtaining a better fit when certain data sets are included.

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Weak cosmic growth in coupled dark energy with a Lagrangian formulation

Cited by 32 publications

References 98 publications

Probing elastic interactions in the dark sector and the role of S8

Probing elastic interactions in the dark sector and the role of S8

Growth of Matter Perturbations in an Interacting Dark Energy Scenario Emerging from Metric-Scalar-Torsion Couplings

Momentum transfer models of interacting dark energy

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