Observational constraints on emergent universe model with non-linear viscous fluid

Paul, Bikash Chandra; Chanda, A.

doi:10.1007/s10714-019-2551-0

Cited by 6 publications

(4 citation statements)

References 35 publications

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“…EU model also accommodates the observed universe fairly well [69]. In the literature [70][71][72][73][74][75][76][77][78][79][80][81][82][83], EU model is implemented in a number of gravitational theories and found to work satisfactorily. We demonstrate here the emergent universe [69] model in the usual 4 and in higher dimensions making use of the nEoS with γ = 1 2 which is given by…”

Section: Eu In Flat Backgroundmentioning

confidence: 91%

“…Subsequently, a flat EU model was obtained with nEoS in GR [69]. Flat EU model is also implemented in different theories of gravity [70][71][72][73][74][75][76] with the observed features [77][78][79][80][81][82][83]. The nEoS [69] p = Aρ − B √ ρ o ρ that admits an EU model, permits three different barotropic fluids determined by A and B.…”

Section: Introductionmentioning

confidence: 99%

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Emergent universe in $$D \ge 4$$ dimensions with dynamical wormholes

Paul

2021

Eur. Phys. J. C

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We present a flat emergent universe (EU) in Einstein gravity with non-linear equation of state (nEoS) in the usual four and in higher dimensions. The EU is assumed to evolve from an initial Einstein’s static universe (ESU) in the infinite past. For a homogeneous Ricci scalar we determine the shape function and obtain a new class of dynamical wormholes that permits EU. The nEoS $$p= A\rho -B \sqrt{\rho _o \rho }$$ p = A ρ - B ρ o ρ is equivalent to three different cosmic fluids which is identified with barotropic fluid for a given A. We obtain EU models in flat, closed and open universes and tested the null energy condition (NEC). At the throat of the wormhole which is recognized as the seed of ESU, we tested the NEC for a given size of the neck. As the EU evolves from an asymptotic past and approaches $$t=0$$ t = 0 , it is found that NEC does not respect. This triggers the onset of interactions at $$t=t_i$$ t = t i , and a realistic flat EU scenario can be obtained in four and in higher dimensions. The origin of the ESU at the throat of the wormhole is also explored via a gravitational instanton mechanism. We compare the relative merits of dynamical wormholes for implementing EU.

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Section: Eu In Flat Backgroundmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Emergent universe in $$D \ge 4$$ dimensions with dynamical wormholes

Paul

2021

Eur. Phys. J. C

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“…In a flat background an Emergent Universe model is obtained with a non-linear equation of state [41] which corresponds to ǫ < 0. Recently a number of theoretical aspects of EU model with such non-linear part of the EoS is reported, the non-linear term represents the presence of initial viscosity in the universe [50]. In the literature [33], EU model is implemented in a number of theories of gravity and found to work satisfactorily to encompass the observed universe.…”

Section: A Flat Backgroundmentioning

confidence: 99%

Dynamical Wormholes in Higher Dimensions and the Emergent Universe

Paul

2020

Preprint

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We present dynamical wormholes in higher dimensions which admit flat emergent universe (EU) model in an elegant way. The EU model was proposed to get rid of some of the problems of the Big Bang cosmology. It is free from initial singularity with other observed features of the universe. The basic assumption of EU model was that the present universe emerged out from a static Einstein universe. In the paper we study EU model in four and in higher dimensions and proposed that the EU originates from a dynamical wormhole and the throat of the wormhole is the seed of the Einstein Static universe. The shape function obtained here admits closed, open and flat universe in higher dimensions. A class of new cosmological solutions in a higher dimensional flat universe is obtained. We obtain shape functions for flat, asymptotic closed and open universe.The shape function obtained here for asymptotic closed universe is new. It is found that flat EU with a non-linear equation of state (EoS) can be accommodated with dynamical wormhole. The non-linear EoS corresponds to three types of fluids in the universe. The EoS parameter is playing an important role in determining the cosmic fluids. The space-time dimensions determines the rate of change of a particular fluid that varies with the scale factor of a dynamically evolving universe with non-interacting fluids. Considering interaction at time t > t0, among the three types of fluids it is possible to describe the observed universe satisfactorily. In a higher dimensional universe it is found that near the throat null energy condition (NEC) is violated, but away from the throat NEC is found to obey admitting the observed universe for a flat case. Another interesting aspect of the EU model is that it permits late accelerating phase. However, in asymptotic closed or open universe, flat emergent universe can be accommodated with NEC which is obeyed right from the throat to the present epoch. The tension at the throat of the wormhole is estimated which is found to depend on the initial size of the Einstein static universe and dimensions of the universe. It is interesting to note that NEC is not violated to accommodate dynamical wormholes for closed or open universe. Although exotic matter is required at the throat for the flat universe, no exotic matter is required for closed or open universe which encompass the emergent universe.

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“…The validity of EU model is studied using recent cosmological observations with the estimation of the observational constraints on the model parameters [74][75][76]. Recently [77] studied the EU scenario described by a nEoS in addition to viscosity. The observational bounds of the model parameters are determined.…”

Section: Introductionmentioning

confidence: 99%

Dynamical stability and phase space analysis of an emergent Universe with non-interacting and interacting fluids

Roy,

Chanda,

Paul

2024

Class. Quantum Grav.

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We investigate the evolution of a flat Emergent Universe obtained with a non-linear equation of state (nEoS) in Einstein's general theory of Relativity. The nEoS is equivalent to three different types of barotropic cosmic fluids, which are found from the nEoS parameter. The EU began expanding initially with no interactions among the cosmic fluids. However, one can assume an interaction that sets in at a time $t \geq t_i$ in the cosmic fluids, we study the evolution of the EU that accommodates the present observed universe. We adopt dynamical system analysis to study the critical points of the autonomous system and the evolutionary behavior of an EU with or without interaction among the cosmic fluid components. We also study the stability of critical points and plot the phase portraits. The density parameters and the corresponding cosmological parameters are determined for both the non-interacting and interacting phases of the evolutionary dynamics of the universe.

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Observational constraints on emergent universe model with non-linear viscous fluid

Cited by 6 publications

References 35 publications

Emergent universe in $$D \ge 4$$ dimensions with dynamical wormholes

Emergent universe in $$D \ge 4$$ dimensions with dynamical wormholes

Dynamical Wormholes in Higher Dimensions and the Emergent Universe

Dynamical stability and phase space analysis of an emergent Universe with non-interacting and interacting fluids

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