Current observations with a decaying cosmological constant allow for chaotic cyclic cosmology

Ellis, George; Platts, Emma; Sloan, David; Weltman, Amanda

doi:10.1088/1475-7516/2016/04/026

Cited by 19 publications

(13 citation statements)

References 107 publications

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“…On the other hand, the cyclic model presented in [69] achieves viability by introducing a negative scalar field potential and a coupling of this postulated field with radiation and matter densities -which are however also motivated by string theory. Recently, the original Tolmann's idea of cyclic cosmology based on a closed Universe has been revisited in [70] using a phase plane analysis, with the addition of decaying cosmological term, and where also the coupling with a scalar field has been introduced. The reconstruction of different f (R) functions leading to cyclic solutions, corresponding to some of the previously mentioned models, was analysed in [71].…”

Section: Models Of Cyclic Cosmologymentioning

confidence: 99%

Cyclic cosmology in modified gravity

Pavlović

Sossich

2017

Phys. Rev. D

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In this work we propose a new general model of eternal cyclic Universe. We start from the assumption that quantum gravity corrections can be effectively accounted by the addition of higher order curvature terms in the Lagrangian density for gravity. It is also taken into account that coefficients associated with these curvature corrections will in general be dependent on a curvature regime. We therewith assume no new ingredients, such as extra dimensions, new scalar fields, phantom energy or special space-time geometries. Evolution of the Universe in this framework is studied and general properties of each phase of the cycle -cosmological bounce, low curvature (ΛCDM) phase, destruction of bounded systems and contracting phase -are analysed in detail. Focusing on some simple special cases, we obtain analytical and numerical solutions for the each phase confirming our analysis.

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Section: Models Of Cyclic Cosmologymentioning

confidence: 99%

Cyclic cosmology in modified gravity

Pavlović

Sossich

2017

Phys. Rev. D

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“…Finally we note that in order to match with observations of our universe it is not necessary that the entire universe bounce, but that at least a single patch of approximately size corresponding to the Hubble radius during inflation bounces. As such we can consider the scenario discussed in [24] in which initial conditions are set far in the past for an inhomogeneous universe. If the inhomogeneities are randomly distributed in a large universe, the majority of any section of a spatial neighborhood may be dominated by their inhomogeneities during collapse.…”

Section: Background Dynamicsmentioning

confidence: 99%

T -model inflation and bouncing cosmology

2020

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We examine the dynamics of a closed cosmology whose matter source is that of a conformally coupled scalar field with a broken SO(1, 1) symmetry, which correspond to the α-attractors proposed by Linde and Kallosh. Following a field redefinition, such models give rise to "T-model" inflationary potentials, whose dynamics provide both an inflationary phase and a classical bounce. We show that the universe can undergo bounces far from the regime of quantum gravity (i.e. at energy densities lower than the Planck density). We analyse perturbations on this background with particular attention given to the effects of a double-bouncing scenario (with rapid recollapse between bounces) on the long wavelength modes. We demonstrate that the predictions of such models agree well with observations and might explain the suppression of power in the low multiples of the CMB.

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“…We can treat the dynamical system (86)-(87) as a sewn dynamical system [47,48]. In this case, we divide the phase portrait into two parts: the first part is for a < a sing and the second part is for a > a sing .…”

Section: Singularities In the Starobinsky Model In The Palatini Formamentioning

confidence: 99%

Starobinsky cosmological model in Palatini formalism

Stachowski

Szydłowski

Borowiec³

2017

Eur. Phys. J. C

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We classify singularities in FRW cosmologies, which dynamics can be reduced to the dynamical system of the Newtonian type. This classification is performed in terms of the geometry of a potential function if it has poles. At the sewn singularity, which is of a finite scale factor type, the singularity in the past meets the singularity in the future. We show that such singularities appear in the Starobinsky model in f (R) =R + γR 2 in the Palatini formalism, when dynamics is determined by the corresponding piecewise-smooth dynamical system. As an effect we obtain a degenerate singularity. Analytical calculations are given for the cosmological model with matter and the cosmological constant. The dynamics of model is also studied using dynamical system methods. From the phase portraits we find generic evolutionary scenarios of the evolution of the universe. For this model, the best fit value of γ = 3γ H 2 0 is equal 9.70 × 10 −11 . We consider a model in both Jordan and Einstein frames. We show that after transition to the Einstein frame we obtain both the form of the potential of the scalar field and the decaying Lambda term.

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Current observations with a decaying cosmological constant allow for chaotic cyclic cosmology

Cited by 19 publications

References 107 publications

Cyclic cosmology in modified gravity

Cyclic cosmology in modified gravity

T -model inflation and bouncing cosmology

Starobinsky cosmological model in Palatini formalism

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