Bounce universe induced by an inhomogeneous dark fluid coupled with dark matter

Brevik, Iver; Обухов, В. В.; Тимошкин, А. В.

doi:10.1142/s0217732314500783

Cited by 24 publications

(25 citation statements)

References 44 publications

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“…7 for the case B corresponding to the different values of d present in Tab. II were calculated with the parameters σ = 0.5, α b = 10 −40 , X b = 10 30 and Ω Λ = 1. Also, since we are interested in perturbations at scales near the Hubble radius today, we from here on use Ω d = 1.…”

Section: Numerical Solutions For the Backgroundmentioning

confidence: 99%

Consistent scalar and tensor perturbation power spectra in single fluid matter bounce with dark energy era

2018

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We investigate cosmological scenarios containing one canonical scalar field with an exponential potential in the context of bouncing models, where the bounce happens due to quantum cosmological effects. The only possible bouncing solutions in this scenario (discarding an infinitely fine tuned exception) must have one and only one dark energy phase, either occurring in the contracting era or in the expanding era. Hence, these bounce solutions are necessarily asymmetric. Naturally, the more convenient solution is the one where the dark energy phase happens in the expanding era, in order to be a possible explanation for the current accelerated expansion indicated by cosmological observations. In this case, one has the picture of a Universe undergoing a classical dust contraction from very large scales, the initial repeller of the model, moving to a classical stiff matter contraction near the singularity, which is avoided due to the quantum bounce. The Universe is then launched to a dark energy era, after passing through radiation and dust dominated phases, finally returning to the dust expanding phase, the final attractor of the model. We calculate the spectral indexes and amplitudes of scalar and tensor perturbations numerically, considering the whole history of the model, including the bounce phase itself, without making any approximation or using any matching condition on the perturbations. As the background model is necessarily dust dominated in the far past, the usual adiabatic vacuum initial conditions can be easily imposed in this era. Hence, this is a cosmological model where the presence of dark energy behavior in the Universe does not turn problematic the usual vacuum initial conditions prescription for cosmological perturbation in bouncing models. Scalar and tensor perturbations end up being almost scale invariant, as expected. The background parameters can be adjusted, without fine tunings, to yield the observed amplitude for scalar perturbations, and also for the ratio between tensor and scalar amplitudes, r = T /S 0.1. The amplification of scalar perturbations over tensor perturbations takes place only around the bounce, due to quantum effects, and it would not occur if General Relativity has remained valid throughout this phase. Hence, this is a bouncing model where a single field induces not only an expanding background dark energy phase, but also produces all observed features of cosmological perturbations of quantum mechanical origin at linear order. * anna@cbpf.br † nelsonpn@cbpf.br ‡ sandro@isoftware.com.br observed today in the Cosmic Microwave Background radiation (CMB). Without inflation, these regions would be causally disconnected in a purely Big Bang model. This puzzle is the so called horizon problem, and it does not exist in bouncing models. Since the Universe had a very large period of contraction in the past, there is no limit to the particle horizon (if the fluids dominating the contracting phase satisfy the strong energy condition). Another puzzle of a purely Big Bang scenario is the ...

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Section: Numerical Solutions For the Backgroundmentioning

confidence: 99%

Consistent scalar and tensor perturbation power spectra in single fluid matter bounce with dark energy era

2018

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“…An inhomogeneous time-dependent EoS for the dark energy has also been discussed as the corresponding fluid-like description of modified theories of gravity (see [6]). In particular, inhomogeneous viscous fluids [7][8][9] were investigated in order to obtain bouncing solutions [10][11][12], leading to a bouncing cosmology. A common method of these articles consists in proposing different Ansatzes for the scale factor a(t)-displaying a bouncing behavior-which leads as a consequence to particular equations of state.…”

Section: Introductionmentioning

confidence: 99%

Bouncing solutions from generalized EoS

2017

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We present an exact analytical bouncing solution for a closed universe filled with only one exotic fluid with negative pressure, obeying a generalized equation of state (GEoS) of the form p(ρ) = Aρ + Bρ λ , where A, B and λ are constants. In our solution A = −1/3, λ = 1/2, and B < 0 is kept as a free parameter. For particular values of the initial conditions, we find that our solution obeys the null energy condition (NEC), which allows us to reinterpret the matter source as that of a real scalar field, φ, with a positive kinetic energy and a potential V (φ). We numerically compute the scalar field as a function of time as well as its potential V (φ), and we find an analytical function for the potential that fits very accurately with the numerical data obtained. The shape of this potential can be well described by a Gaussian-type of function, and hence there is no spontaneous symmetry minimum of V (φ). We show numerically that the bouncing scenario is structurally stable in a small vicinity of the value A = −1/3. We also include the study of the evolution of the linear fluctuations due to linear perturbations in the metric. These perturbations show an oscillatory behavior near the bouncing and approach a constant at large scales.

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“…[31][32][33]. In the papers [34,35] a bounce cosmology induced by an inhomogeneous viscous fluid in FRW space-time was investigated. In Ref.…”

Section: Introductionmentioning

confidence: 99%

Viscous coupled fluids in inflationary cosmology

Brevik

Тимошкин

2016

J. Exp. Theor. Phys.

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We consider the inflation produced by two coupled fluids in the flat Friedmann-Robertson-Walker universe. Different cosmological models for describing inflation by use of an inhomogeneous equation of state for the fluid are investigated. The gravitational equations for energy and matter are solved, and analytic representations for the Hubble parameter and the energy density are obtained. Corrections in the energy density for matter inducing the inflation and the coupling with energy are discussed. We analyze the description of inflation induced by non-constant equation-of-state parameters from fluid viscosity. The correspondence between the spectral index and the tensor-to-scalar ratio recently observed by the Planck satellite is considered.PACS numbers: 98.80.-k, 95.36.+x

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Bounce universe induced by an inhomogeneous dark fluid coupled with dark matter

Cited by 24 publications

References 44 publications

Consistent scalar and tensor perturbation power spectra in single fluid matter bounce with dark energy era

Consistent scalar and tensor perturbation power spectra in single fluid matter bounce with dark energy era

Bouncing solutions from generalized EoS

Viscous coupled fluids in inflationary cosmology

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