Variable sound speed in interacting dark energy models

Linton, Mark S.; Pourtsidou, Alkistis; Crittenden, Robert; Maartens, Roy

doi:10.1088/1475-7516/2018/04/043

Cited by 38 publications

(44 citation statements)

References 47 publications

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“…These results allow to give necessary conditions on the function b(r )/r but they are not sufficient to show that the form of b(r ) is of the form of a polynomial. To ensure this hypothesis, we assume that the sound speed, i.e., the variation of the pressure with respect to the density is negligibly small [38]. Combining this additional requirement, we stabilize the solution as we shall show below.…”

Section: F (R) Wormholes With Rational Shape Functionmentioning

confidence: 99%

Traversable wormholes with vanishing sound speed in f(R) gravity

2021

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We derive exact traversable wormhole solutions in the framework of f(R) gravity with no exotic matter and with stable conditions over the geometric fluid entering the throat. For this purpose, we propose power-law f(R) models and two possible approaches for the shape function b(r)/r. The first approach makes use of an inverse power-law function, namely $$b(r)/r\sim r^{-1-\beta }$$ b ( r ) / r ∼ r - 1 - β . The second one adopts Padé approximants, used to characterize the shape function in a model-independent way. We single out the P(0, 1) approximant where the fluid perturbations are negligible within the throat, if the sound speed vanishes at $$r=r_0$$ r = r 0 . The former guarantees an overall stability of the geometrical fluid into the wormhole. Finally, we get suitable bounds over the parameters of the model for the above discussed cases. In conclusion, we find that small deviations from general relativity give stable solutions.

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Section: F (R) Wormholes With Rational Shape Functionmentioning

confidence: 99%

Traversable wormholes with vanishing sound speed in f(R) gravity

2021

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“…The velocity of sound plays a similar role to that of equation of state for the background cosmology, which relates the pressure and density as in [53],…”

Section: B Velocity Of Soundmentioning

confidence: 99%

Effective equation of state in modified gravity and observational constraints

Arora

Meng

Pacif

et al. 2020

Class. Quantum Grav.

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In this article, the bulk viscosity is introduced in a modified gravity model. The gravitational action has a general f (R, T) form, where R and T are the curvature scalar and the trace of energy momentum tensor respectively. An effective equation of state (EoS) has been investigated in the cosmological evolution with bulk viscosity. In the present scenario, the Hubble parameter which has a scaling relation with the redshift can be obtained generically. The role of deceleration parameter q and equation of state parameter ω is discussed to explain the late-time accelerating expansion of the universe. The statefinder parameters and Om diagnostic analysis are discussed for our obtained model to distinguish from other dark energy models together with the analysis of energy conditions and velocity of sound for the model. We have also numerically investigated the model by detailed maximum likelihood analysis of 580 Type Ia supernovae from Union 2.1 compilation datasets and updated 57 Hubble datasets (31 data points from differential age method and 26 points from BAO and other methods). It is with efforts found that the present model is in good agreement with observations.

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“…A further analysis on the effective speed of sound parameter is performed in [44], where the authors consider the contribution of matter (Baryonic and dark matter (DM)), photons and neutrinos to get, for example, a probability distribution for the c 2 s value. In [45], a new class of DM-DE interacting models is identified. The authors study the implications of a varying effective speed of sound on the Cosmic Microwave Background (CMB) and the matter power spectrum.…”

Section: Introductionmentioning

confidence: 99%

A varying dark energy effective speed of sound parameter in the phantom Universe

2021

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We analyse the phenomenological effects of a varying Dark Energy (DE) effective speed of sound parameter, $$c^{2}_{\text {sd}}$$ c sd 2 , on the cosmological perturbations of three phantom DE models. Each of these models induce a particular abrupt future event known as Big Rip (BR), Little Rip (LR), and Little Sibling of the Big Rip (LSBR). In this class of abrupt events, all the bound structures in the Universe would be ripped apart at a finite cosmic time. We compute the evolution of the perturbations, $$f\sigma _{8}$$ f σ 8 growth rate and forecast the current matter power spectrum. We vary the $$c^{2}_{\text {sd}}$$ c sd 2 parameter in the interval [0, 1] and compute the relative deviation with respect $$c^{2}_{\text {sd}}=1$$ c sd 2 = 1 . In addition, we analyse the effect of gravitational potential sign flip that occurs at very large scale factors as compared with the current one.

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Variable sound speed in interacting dark energy models

Cited by 38 publications

References 47 publications

Traversable wormholes with vanishing sound speed in f(R) gravity

Traversable wormholes with vanishing sound speed in f(R) gravity

Effective equation of state in modified gravity and observational constraints

A varying dark energy effective speed of sound parameter in the phantom Universe

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