scholarly journals Reconstruction Procedure in Modified Gravity Cosmological Models

2014 ◽  
Author(s):  
Sergey Voronov
Keyword(s):  
Modified Gravity ◽  
Cosmological Models ◽  
Reconstruction Procedure

Anisotropic bulk viscous cosmological models in a modified gravity

2013 ◽  
Vol 350 (1) ◽  
pp. 375-380 ◽  
Author(s):  
D. R. K. Reddy ◽  
R. Bhuvana Vijaya ◽  
T. Vidya Sagar ◽  
R. L. Naidu
Keyword(s):  
Modified Gravity ◽  
Cosmological Models ◽  
Bulk Viscous

scholarly journals Relic gravitational waves in cosmological models based on the modified gravity theories

2021 ◽  
Vol 2081 (1) ◽  
pp. 012002
Author(s):  
I V Fomin ◽  
S V Chervon
Keyword(s):  
Energy Density ◽  
Gravitational Waves ◽  
Modified Gravity ◽  
Direct Detection ◽  
Cosmological Models ◽  
Observational Constraints ◽  
Cosmological Perturbations ◽  
Modified Gravity Theories ◽  
Relic Gravitational Waves ◽  
Gravity Theories

Abstract We consider cosmological models based on the generalized scalar-tensor gravity, which correspond to the observational constraints on the parameters of cosmological perturbations for any model’s parameters. The estimates of the energy density of relic gravitational waves for such a cosmological models were made. The possibility of direct detection of such a gravitational waves using modern and prospective methods was discussed as well.

scholarly journals Superpotential method for chiral cosmological models connected with modified gravity

2019 ◽  
Vol 100 (6) ◽  
Author(s):  
S. V. Chervon ◽  
I. V. Fomin ◽  
E. O. Pozdeeva ◽  
M. Sami ◽  
S. Yu. Vernov
Keyword(s):  
Modified Gravity ◽  
Cosmological Models ◽  
Superpotential Method

scholarly journals Integrable cosmological models with an additional scalar field

2021 ◽  
Vol 81 (11) ◽  
Author(s):  
Vsevolod R. Ivanov ◽  
Sergey Yu. Vernov
Keyword(s):  
Scalar Field ◽  
Cosmological Constant ◽  
Gravity Model ◽  
Modified Gravity ◽  
Field Model ◽  
Cosmic Time ◽  
Cosmological Models ◽  
Conformal Metric ◽  
General Solutions ◽  
Hubble Parameters

AbstractWe consider modified gravity cosmological models that can be transformed into two-field chiral cosmological models by the conformal metric transformation. For the $$R^2$$ R 2 gravity model with an additional scalar field and the corresponding two-field model with the cosmological constant and nonstandard kinetic part of the action, the general solutions have been obtained in the spatially flat FLRW metric. We analyze the correspondence of the cosmic time solutions obtained and different possible evolutions of the Hubble parameters in the Einstein and Jordan frames.

scholarly journals Cosmological models with squared trace in modified gravity

2020 ◽  
Vol 29 (15) ◽  
pp. 2050100
Author(s):  
B. Mishra ◽  
S. K. Tripathy ◽  
Saibal Ray
Keyword(s):  
Modified Gravity ◽  
Hubble Parameter ◽  
Energy Momentum Tensor ◽  
Cosmological Parameters ◽  
Momentum Tensor ◽  
Scale Factor ◽  
Specific Form ◽  
Cosmological Models ◽  
Modified Theory Of Gravity ◽  
Modified Theory

In this work, we present a few simple cosmological models under the modified theory of gravity in the particular form of [Formula: see text], where [Formula: see text] is the Ricci Scalar and [Formula: see text] is the trace of the energy–momentum tensor. Two special cosmological models are studied with (i) hyperbolic scale factor and (ii) specific form of the Hubble parameter. The models are observed to predict relevant cosmological parameters closer to the observational values. Both the models reduce to overlap with the [Formula: see text]CDM model at late times. We have discussed some interesting results related to wormhole solutions as evolved from our model. The possible occurrence of Big Trip in wormholes for the models are also discussed.

scholarly journals Cosmological models in modified gravity theories with extended nonminimal derivative couplings

2017 ◽  
Vol 95 (4) ◽  
Author(s):  
Tiberiu Harko ◽  
Francisco S. N. Lobo ◽  
Emmanuel N. Saridakis ◽  
Minas Tsoukalas
Keyword(s):  
Modified Gravity ◽  
Cosmological Models ◽  
Modified Gravity Theories ◽  
Gravity Theories

Some late-time cosmological aspects of a Gauss–Bonnet gravity with nonminimal coupling à la Brans–Dicke: solutions and perspectives

2013 ◽  
Vol 91 (4) ◽  
pp. 300-321 ◽  
Author(s):  
Rami Ahmad El-Nabulsi
Keyword(s):  
Scalar Field ◽  
String Theory ◽  
Modified Gravity ◽  
Cosmological Models ◽  
Gravity Theory ◽  
Accelerating Universe ◽  
Late Time ◽  
Nonminimal Coupling ◽  
Bonnet Gravity ◽  
Time Dynamics

In this paper, we study modified homogeneous and isotropic cosmological models based on the Gauss–Bonnet invariant term as models of an accelerating universe. We discuss and criticize the late-time dynamics of six independent cosmological models: in the first model, we discuss the case of the modified gravity f(R) ∝ R1+δ for δ = −1/2 and 1 augmented by the Gauss–Bonnet invariant term; in the second model, we discuss the general case of f(R) ∝ R1+δ accompanied by a nonminimal coupling between the scalar field and the Ricci curvature as well as the Gauss–Bonnet invariant; in the third model, we discuss a generalized modified gravity model that includes the Einstein–Hilbert action, a dynamical cosmological constant, and an effective gravitational coupling constant; in the fourth model, we discuss a more generalized modified scalar–tensor cosmology that includes in addition to the Gauss–Bonnet invariant term, stringy corrections motivated from string and heterotic superstring arguments; in the fifth model, we discuss the cosmological dynamics of a nonminimal scalar Gauss–Bonnet gravity theory motivated from string theory; and finally in the sixth model, we discuss the possibility of having an extension of the generalized modified gravity theory, free from nonminimal coupling with δ = 0, with a Hubble expansion rate and an equation of state parameter that depend on the Gauss–Bonnet invariant term. In the first five models, we conjecture that the Hubble parameter is related to the scalar field by the relation [Formula: see text], which is applied merely to the late time epoch. This ansatz is in fact motivated by some recent advances in scalar–tensor theory and string theory. All of the six models reveal interesting consequences, which are discussed in some detail. Our main objective in this work is to analyze, criticize, and differentiate between viable realistic models and those that are not. Many critical points are discussed in some detail.

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