Cosmological dynamics of mimetic gravity

Dutta, Jibitesh; Khyllep, Wompherdeiki; Saridakis, Emmanuel N.; Tamanini, Nicola; Vagnozzi, Sunny

doi:10.1088/1475-7516/2018/02/041

Cited by 111 publications

(75 citation statements)

References 164 publications

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“…For relevant recent work one can also see [42,43]. Again, it is interesting to observe that negative energy density does not always imply phantom behavior in general (one can see [40], [43] From the above constraint equation (22), it can be seen that one of the dimensionless density parameters is linearly independent. Then the above governing cosmological equations (8)-(11) can be recast into a following onedimensional system:…”

Section: Dynamical System Analysis Of Rastall Modelmentioning

confidence: 88%

Linear growth index of matter perturbations in Rastall gravity

Khyllep

Dutta

2019

Physics Letters B

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Rastall gravity theory shows notable features consistent with physical observations in comparison to the standard Einstein theory. Recently, there has been a debate about the equivalence of Rastall gravity and general relativity.Motivated by this open issue, in the present work, we attempt to shed some light on this debate by analyzing the evolution of the Rastall based cosmological model at the background as well as perturbation level. Employing the dynamical system techniques, we found that at late times, the dynamics of the model resembles the ΛCDM model at the background level irrespective of the choice of Rastall's parameter. However, at the perturbation level, we found that the evolution of the growth index heavily depends on the Rastall's parameter and displays a significant deviation from the ΛCDM model. arXiv:1907.09221v1 [gr-qc]

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Section: Dynamical System Analysis Of Rastall Modelmentioning

confidence: 88%

Linear growth index of matter perturbations in Rastall gravity

Khyllep

Dutta

2019

Physics Letters B

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“…3 Other scenarios worth mentioning include the possibility that properly accounting for cosmic variance (due to the fact that a limited sample of the Hubble flow is observed) enlarges the DM and DE beyond the purely gravitational ones are not forbidden by any fundamental symmetry in nature [118][119][120][121][122][123] and could help addressing the so called coincidence or why now? problem [124][125][126][127][128] , see e.g. and Ref.…”

Section: Introductionmentioning

confidence: 99%

Nonminimal dark sector physics and cosmological tensions

et al. 2020

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We explore whether non-standard dark sector physics might be required to solve the existing cosmological tensions. The properties we consider in combination are: (a) an interaction between the dark matter and dark energy components, and (b) a dark energy equation of state w different from that of the canonical cosmological constant w = −1. In principle, these two parameters are independent. In practice, to avoid early-time, superhorizon instabilities, their allowed parameter spaces are correlated. Moreover, a clear degeneracy exists between these two parameters in the case of Cosmic Microwave Background (CMB) data. We analyze three classes of extended interacting dark energy models in light of the 2019 Planck CMB results and Cepheid-calibrated local distance ladder H0 measurements of Riess et al. (R19), as well as recent Baryon Acoustic Oscillation (BAO) and Type Ia Supernovae (SNeIa) distance data. We find that in quintessence coupled dark energy models, where w > −1, the evidence for a non-zero coupling between the two dark sectors can surpass the 5σ significance. Moreover, for both Planck+BAO or Planck+SNeIa, we found a preference for w > −1 at about three standard deviations. Quintessence models are, therefore, in excellent agreement with current data when an interaction is considered. On the other hand, in phantom coupled dark energy models, there is no such preference for a non-zero dark sector coupling. All the models we consider significantly raise the value of the Hubble constant easing the H0 tension. In the interacting scenario, the disagreement between Planck+BAO and R19 is considerably reduced from 4.3σ in the case of ΛCDM to about 2.5σ. The addition of low-redshift BAO and SNeIa measurements leaves, therefore, some residual tension with R19 but at a level that could be justified by a statistical fluctuation. We conclude that non-minimal dark energy cosmologies, such as coupled quintessence or phantom models, may soften the existing cosmological tensions. * eleonora.divalentino@manchester.ac.uk † alessandro.melchiorri@roma1.infn.it ‡ omena@ific.uv.es § sunny.vagnozzi@ast.cam.ac.uk 1 In Ref. [15,16] the reader can find complete reviews comparing the CMB and local determinations of H 0 .

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“…On the other hand, several DE models rely on the introduction of a new fluid, possibly through a very light field (see for example [37,38,39,40,41,42,43,44,45,46,47]), or through modifications to GR (see e.g. [48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63]). Although within most dark sector models the two dark components do not interact, an interesting class of cosmological models (usually referred to as coupled DE) feature interactions between DM and DE (see for example [64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,…”

Section: Introductionmentioning

confidence: 99%

Dawn of the dark: unified dark sectors and the EDGES Cosmic Dawn 21-cm signal

Yang

Pan

Vagnozzi

et al. 2019

J. Cosmol. Astropart. Phys.

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While the origin and composition of dark matter and dark energy remains unknown, it is possible that they might represent two manifestations of a single entity, as occurring in unified dark sector models. On the other hand, advances in our understanding of the dark sector of the Universe might arise from Cosmic Dawn, the epoch when the first stars formed. In particular, the first detection of the global 21-cm absorption signal at Cosmic Dawn from the EDGES experiment opens up a new arena wherein to test models of dark matter and dark energy. Here, we consider generalized and modified Chaplygin gas models as candidate unified dark sector models. We first constrain these models against Cosmic Microwave Background data from the Planck satellite, before exploring how the inclusion of the global 21-cm signal measured by EDGES can improve limits on the model parameters, finding that the uncertainties on the parameters of the Chaplygin gas models can be reduced by a factor between 1.5 and 10. We also find that within the generalized Chaplygin gas model, the tension between the CMB and local determinations of the Hubble constant H0 is reduced from ≈ 4σ to ≈ 1.3σ. In conclusion, we find that the global 21-cm signal at Cosmic Dawn can provide an extraordinary window onto the physics of unified dark sectors.

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Cosmological dynamics of mimetic gravity

Cited by 111 publications

References 164 publications

Linear growth index of matter perturbations in Rastall gravity

Linear growth index of matter perturbations in Rastall gravity

Nonminimal dark sector physics and cosmological tensions

Dawn of the dark: unified dark sectors and the EDGES Cosmic Dawn 21-cm signal

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