Observational constraints on the model parameters of a class of emergent universe

Ghose, Subrata; Thakur, P.; Paul, Bikash Chandra

doi:10.1111/j.1365-2966.2011.19743.x

Cited by 13 publications

(14 citation statements)

References 26 publications

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“…The presence of such a pre-inflationary phase in the EU scenario has observable consequences, namely on the anisotropies within the CMB spectrum at large scales, see e.g., [161][162][163]. Utilizing the recently developed state-finder parameters, the behavior of different stages of the evolution of the EU model has been studied and it is shown that the universe starts from an asymptotic ES state and goes to the CDM model [66] (for a systematic analysis of EU scenario, its transition to slow-roll inflation through a period of super-inflationary regime, see [164][165][166] and the references therein). In the current study, we observed that the equilibrium point for case iii could be stable or unstable depending on the value of w parameter.…”

Section: Discussionmentioning

confidence: 99%

Stability of the Einstein static universe in f(R, T) gravity

Shabani¹,

Ziaie²

2017

Eur. Phys. J. C

132

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The Einstein static (ES) universe has played a major role in various emergent scenarios recently proposed in order to cure the problem of the initial singularity of the standard model of cosmology. In the model we address, we study the existence and stability of an ES universe in the context of f (R, T ) modified theories of gravity. Considering specific forms of the f (R, T ) function, we seek for the existence of solutions representing ES state. Using dynamical system techniques along with numerical analysis, we find two classes of solutions: the first one is always unstable of the saddle type, while the second is always stable so that its dynamical behavior corresponds to a center equilibrium point. The importance of the second class of solutions is due to the significant role they play in constructing non-singular emergent models in which the universe could have experienced past-eternally a series of infinite oscillations about such an initial static state after which it enters, through a suitable physical mechanism, to an inflationary era. Considering specific forms for the functionality of f (R, T ), we show that this theory is capable of providing cosmological solutions which admit emergent universe (EU) scenarios. We also investigate homogeneous scalar perturbations for the mentioned models. The stability regions of the solutions are parametrized by a linear equation of state (EoS) parameter and other free parameters that will be introduced for the models. Our results suggest that modifications in f (R, T ) gravity would lead to stable solutions which are unstable in f (R) gravity model.

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Section: Discussionmentioning

confidence: 99%

Stability of the Einstein static universe in f(R, T) gravity

Shabani¹,

Ziaie²

2017

Eur. Phys. J. C

132

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“…During the SDSS survey spectroscopic samples were retrieved from thousands of red galaxies that spanned across the sky, covering a diameter of around five billion light yeras. The BAO peak parameter is defined as (Thakur, Ghose & Paul 2009;Paul, Thakur & Ghose 2010;Paul, Ghose & Thakur 2011;Ghose, Thakur & Paul 2012):…”

Section: B Joint Analysis With Cc+baomentioning

confidence: 99%

“…(Wu & Yu 2007;Thakur, Ghose & Paul 2009;Paul, Thakur & Ghose 2010;Paul, Ghose & Thakur 2011;Ghose, Thakur & Paul 2012) …”

mentioning

confidence: 99%

Constraints on Cubic and $f(P)$ Gravity from the Cosmic Chronometers, BAO & CMB datasets : Use of Machine Learning Algorithms

Giri,

Rudra

2021

Preprint

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In this work we perform an observational data analysis on Einsteinian cubic gravity and f (P ) gravity with the objective of constraining the parameter space of the theories. We use the 30 point z − H(z) cosmic chronometer data as the observational tool for our analysis along with the BAO and the CMB peak parameters. The χ 2 statistic is used for the fitting analysis and it is minimized to obtain the best fit values for the free model parameters. We have used the Markov chain Monte Carlo algorithm to obtain bounds for the free parameters. To achieve this we used the publicly available CosmoMC code to put parameter bounds and subsequently generate contour plots for them with different confidence intervals. Besides finding the Hubble parameter H in terms of the redshift z theoretically from our gravity models, we have exercised correlation coefficients and two machine learning models, namely the linear regression (LR) and artificial neural network (ANN), for the estimation of H(z). For this purpose, we have developed a Python package for finding the parameter space, performing the subsequent statistical analysis and prediction analysis using machine learning. We compared both of our theoretical and estimated values of H(z) with the observations. It is seen that our theoretical and estimated models from machine learning performed significantly well when compared with the observations.

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“…This model (2.1) can produce a emergent universe without the time singularity [43][44][45][46]. But in this paper, we will take this RMCG fluid as the dark components in our Universe.…”

Section: Dark Models In Rmcg Cosmologymentioning

confidence: 99%

Reduced modified Chaplygin gas cosmology

Geng

et al. 2015

J. High Energ. Phys.

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Abstract:In this paper, we study cosmologies containing the reduced modified Chaplygin gas (RMCG) fluid which is reduced from the modified Chaplygin gas p = Aρ − Bρ −α for the value of α = −1/2. In this special case, dark cosmological models can be realized for different values of model parameter A. We investigate the viabilities of these dark cosmological models by discussing the evolutions of cosmological quantities and using the currently available cosmic observations. It is shown that the special RMCG model (A = 0 or A = 1) which unifies the dark matter and dark energy should be abandoned. For A = 1/3, RMCG which unifies the dark energy and dark radiation is the favorite model according to the objective Akaike information criteria. In the case of A < 0, RMCG can achieve the features of the dynamical quintessence and phantom models, where the evolution of the universe is not sensitive to the variation of model parameters.

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Observational constraints on the model parameters of a class of emergent universe

Cited by 13 publications

References 26 publications

Stability of the Einstein static universe in f(R, T) gravity

Stability of the Einstein static universe in f(R, T) gravity

Constraints on Cubic and $f(P)$ Gravity from the Cosmic Chronometers, BAO & CMB datasets : Use of Machine Learning Algorithms

Reduced modified Chaplygin gas cosmology

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