scholarly journals Cosmology in the mimetic higher-curvature $$f(R,R_{\mu \nu }R^{\mu \nu })$$ gravity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Adam Z. Kaczmarek ◽  
Dominik Szczȩśniak

AbstractIn the framework of the mimetic approach, we study the $$f(R,R_{\mu \nu }R^{\mu \nu })$$ f ( R , R μ ν R μ ν ) gravity with the Lagrange multiplier constraint and the scalar potential. We introduce field equations for the discussed theory and overview their properties. By using the general reconstruction scheme we obtain the power law cosmology model for the $$f(R,R_{\mu \nu }R^{\mu \nu })=R+d(R_{\mu \nu }R^{\mu \nu })^p$$ f ( R , R μ ν R μ ν ) = R + d ( R μ ν R μ ν ) p case as well as the model that describes symmetric bounce. Moreover, we reconstruct model, unifying both matter dominated and accelerated phases, where ordinary matter is neglected. Using inverted reconstruction scheme we recover specific $$f(R,R_{\mu \nu }R^{\mu \nu })$$ f ( R , R μ ν R μ ν ) function which give rise to the de-Sitter evolution. Finally, by employing the perfect fluid approach, we demonstrate that this model can realize inflation consistent with the bounds coming from the BICEP2/Keck array and the Planck data. We also discuss the holographic dark energy density in terms of the presented $$f(R,R_{\mu \nu }R^{\mu \nu })$$ f ( R , R μ ν R μ ν ) theory. Thus, it is suggested that the introduced extension of the mimetic regime may describe any given cosmological model.

2008 ◽  
Vol 17 (12) ◽  
pp. 2219-2228 ◽  
Author(s):  
M. R. SETARE

In this paper, we investigate cosmological application of holographic dark energy density in the modified gravity framework. We employ the holographic model of dark energy to obtain the equation of state for the holographic energy density in a spatially flat universe. Our calculation shows that, taking ΩΛ = 0.73 for the present time, it is possible to have wΛ crossing -1. This implies that one can generate a phantom-like equation of state from a holographic dark energy model in flat universe in the modified gravity cosmology framework. Also, we develop a reconstruction scheme for the modified gravity with f(R) action.


2015 ◽  
Vol 12 (10) ◽  
pp. 1550119 ◽  
Author(s):  
S. Davood Sadatian

We obtain interacting holographic dark energy density in the framework of vector field cosmology (LIV). We consider possible modification of equation of state for the holographic energy density in lorentz invariance violation cosmology. In this case we select Jeans length as the IR cut-off in the holographic model. Then we consider the interaction between holographic energy densities ρΛ and ρm in this framework.


2012 ◽  
Vol 21 (12) ◽  
pp. 1250091 ◽  
Author(s):  
ORLANDO LUONGO ◽  
LUCA BONANNO ◽  
GERARDO IANNONE

Motivated by recent works on the role of the holographic principle in cosmology, we relate a class of second-order Ricci invariants to the IR cutoff characterizing the holographic dark energy density. The choice of second-order invariants provides an invariant way to account the problem of causality for the correct cosmological cutoff, since the presence of event horizons is not an a priori assumption. We find that these models work fairly well, by fitting the observational data, through a combined cosmological test with the use of SNeIa, BAO and CMB. This class of models is also able to overcome the fine-tuning and coincidence problems. Finally, to make a comparison with other recent models, we adopt the statistical tests AIC and BIC.


2000 ◽  
Vol 15 (16) ◽  
pp. 1023-1029 ◽  
Author(s):  
ZONG-HONG ZHU

By using the comoving distance, we derive an analytic expression for the optical depth of gravitational lensing, which depends on the redshift to the source and the cosmological model characterized by the cosmic mass density parameter Ωm, the dark energy density parameter Ωm and its equation of state ωx = px/ρx. It is shown that, the larger the dark energy density and the more negative its pressure, the higher is the gravitational lensing probability. This fact can provide an independent constraint for dark energy.


2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
Pablo Alejandro Sánchez ◽  
Mauricio Bellini

We explore the possibility that the expansion of the universe can be driven by a condensate of spinors which are free of interactions in a 5D relativistic vacuum defined in an extended de Sitter spacetime which is Riemann flat. The extra coordinate is considered as noncompact. After making a static foliation on the extra coordinate, we obtain an effective 4D (inflationary) de Sitter expansion which describes an inflationary universe. We found that the condensate of spinors studied here could be an interesting candidate to explain the presence of dark energy in the early universe. The dark energy density which we are talking about is poured into smaller subhorizon scales with the evolution of the inflationary expansion.


2019 ◽  
Vol 29 (01) ◽  
pp. 1950176 ◽  
Author(s):  
A. V. Astashenok ◽  
A. S. Tepliakov

Some models of holographic dark energy for Randall–Sundrum brane are considered. For the first class of dark energy models, we take energy density in the form [Formula: see text], where [Formula: see text] is size of event horizon in universe and [Formula: see text] is parameter (Tsallis holographic energy). Analysis of observational data allows to define upper limit on value of [Formula: see text] ([Formula: see text] is current energy density in the universe and [Formula: see text] is brane tension). Then we investigate models for which dark energy density has the form [Formula: see text] where [Formula: see text] is Hubble parameter.


2015 ◽  
Vol 93 (1) ◽  
pp. 68-79
Author(s):  
R. Chaubey ◽  
A.K. Shukla

In this paper, we study the general class of Bianchi cosmological models with holographic dark energy component. We have discussed three types of solutions of the average scale factor for the general class of Bianchi cosmological models by using a special law for the deceleration parameter, which is linear in time with a negative slope. The exact solutions to the corresponding field equations are also obtained. All the physical parameters are calculated and discussed in each physically viable cosmological model. For large time (i.e., t → ∞) the models tend asymptotically to an isotropic Friedmann–Robertson–Walker cosmological model. Quintessence scalar field and quintessence potential are also obtained for three different scenarios of scale factor.


2011 ◽  
Vol 50 (9) ◽  
pp. 2878-2883 ◽  
Author(s):  
Hassan Saadat ◽  
S. N. Mousavi ◽  
A. M. Saadat

2018 ◽  
Vol 33 (15) ◽  
pp. 1850084
Author(s):  
S. Surendra Singh

Considering the locally rotationally symmetric (LRS) Bianchi type-I metric with cosmological constant [Formula: see text], Einstein’s field equations are discussed based on the background of anisotropic fluid. We assumed the condition A = B[Formula: see text] for the metric potentials A and B, where m is a positive constant to obtain the viable model of the Universe. It is found that [Formula: see text] is positive and inversely proportional to time. The values of matter-energy density [Formula: see text], dark energy density [Formula: see text] and deceleration parameter q are found to be consistent with the values of WMAP observations. State finder parameters and anisotropic deviation parameter are also investigated. It is also observed that the derived model is an accelerating, shearing and non-rotating Universe. Some of the asymptotic and geometrical behaviors of the derived models are investigated with the age of the Universe.


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