scholarly journals Reconstruction of cosmic history from a simple parametrization of H

2017 ◽  
Vol 14 (07) ◽  
pp. 1750111 ◽  
Author(s):  
Shibesh Kumar Jas Pacif ◽  
Ratbay Myrzakulov ◽  
Shynaray Myrzakul
Keyword(s):  
Hubble Parameter ◽  
Functional Form ◽  
Cosmic Acceleration ◽  
Model Parameters ◽  
Late Time ◽  
Text Data ◽  
Simple Modification ◽  
Big Rip ◽  
Cosmic History

In this paper, we propose a simple parametrization of the Hubble parameter (HP) [Formula: see text] in order to explain the late-time cosmic acceleration. We show that our proposal covers many models obtained in different schemes of parametrization under one umbrella. We demonstrate that a simple modification in the functional form of HP can give rise to interesting cosmological phenomena such as big rip singularity, bounce and others. We have also constrained the model parameters using the latest 28 points of [Formula: see text] data for three cases which admit transition from deceleration to acceleration.

scholarly journals An accelerating cosmological model from a parametrization of Hubble parameter

2019 ◽  
Vol 35 (05) ◽  
pp. 2050011 ◽  
Author(s):  
S. K. J. Pacif ◽  
Md Salahuddin Khan ◽  
L. K. Paikroy ◽  
Shalini Singh
Keyword(s):  
Dark Energy ◽  
Cosmological Model ◽  
Hubble Parameter ◽  
Cosmological Parameters ◽  
Cosmic Time ◽  
Solution Procedure ◽  
Cosmic Acceleration ◽  
Model Parameters ◽  
Late Time ◽  
Field Equations

In view of late-time cosmic acceleration, a dark energy cosmological model is revisited wherein Einstein’s cosmological constant is considered as a candidate of dark energy. Exact solution of Einstein field equations (EFEs) is derived in a homogeneous isotropic background in classical general relativity. The solution procedure is adopted in a model-independent way (or the cosmological parametrization). A simple parametrization of the Hubble parameter (H) as a function of cosmic time t is considered which yields an exponential type of evolution of the scale factor (a) and also shows a negative value of deceleration parameter at the present time with a signature flip from early deceleration to late acceleration. Cosmological dynamics of the model obtained have been discussed illustratively for different phases of the evolution of the universe. The evolution of different cosmological parameters is shown graphically for flat and closed cases of Friedmann–Lemaitre–Robertson–Walker (FLRW) spacetime for the presented model (open case is incompatible to the present scenario). We have also constrained our model parameters with the updated (36 points) observational Hubble dataset.

scholarly journals BIG RIP AND LITTLE RIP SOLUTIONS IN SCALAR MODEL WITH KINETIC AND GAUSS–BONNET COUPLINGS

2012 ◽  
Vol 21 (01) ◽  
pp. 1250002 ◽  
Author(s):  
L. N. GRANDA ◽  
E. LOAIZA
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
Hubble Parameter ◽  
Field Model ◽  
Kinetic Term ◽  
Late Time ◽  
Scalar Model ◽  
Big Rip ◽  
Specific Choice ◽  
Cosmological Solutions

Late time cosmological solutions for scalar field model with kinetic and Gauss–Bonnet couplings are considered. The quintom scenario is realized with and without Big Rip singularity. We find that under specific choice of the Gauss–Bonnet coupling, the model considerably simplifies, giving rise to solutions where the kinetic term is proportional to the square of the Hubble parameter. This allows to reconstruct the model for a suitable cosmological evolution. We considered a solution that matches the observed behavior of the equation of state, while Big Rip singularity may be present or absent, depending on the parameters of the solution. Evolutionary scenarios known as Little Rip, have also been considered.

scholarly journals Cosmic acceleration from coupling of baryonic and dark matter components: Analysis and diagnostics

2019 ◽  
Vol 28 (06) ◽  
pp. 1950083 ◽  
Author(s):  
Abhineet Agarwal ◽  
R. Myrzakulov ◽  
S. K. J. Pacif ◽  
M. Shahalam
Keyword(s):  
Dark Matter ◽  
Degrees Of Freedom ◽  
Cosmic Acceleration ◽  
Jordan Frame ◽  
Model Parameters ◽  
Late Time ◽  
Baryonic Matter ◽  
Acoustic Oscillations ◽  
Type Ia ◽  
Components Analysis

In this paper, we examine a scenario in which late-time cosmic acceleration might arise due to the coupling between baryonic matter and dark matter without the presence of extra degrees of freedom. In this case, one can obtain late-time acceleration in Jordan frame and not in Einstein frame. We consider two different forms of parametrization of the coupling function, and put constraints on the model parameters by using an integrated dataset of Hubble parameter, Type Ia supernova and baryon acoustic oscillations. The models under consideration are consistent with the observations. In addition, we perform the statefinder and [Formula: see text] diagnostics, and show that the models exhibit a distinctive behavior due to the phantom characteristic in future which is a generic feature of the underlying scenario.

scholarly journals Cosmic acceleration sourced by modification of gravity without extra degrees of freedom

2019 ◽  
Vol 16 (08) ◽  
pp. 1950128
Author(s):  
Abhineet Agarwal ◽  
R. Myrzakulov ◽  
S. K. J. Pacif ◽  
M. Sami ◽  
Anzhong Wang
Keyword(s):  
Degrees Of Freedom ◽  
Large Scale ◽  
Cosmic Acceleration ◽  
Jordan Frame ◽  
Model Parameters ◽  
Late Time ◽  
Baryonic Matter ◽  
Narrow Region ◽  
Cluster Data ◽  
Age Constraints

In this paper, we investigate a scenario in which late-time cosmic acceleration might arise due to coupling between dark matter and baryonic matter without resorting to dark energy or large-scale modification of gravity associated with extra degrees of freedom. The scenario can give rise to late-time acceleration in Jordan frame and no acceleration in Einstein frame — generic modification of gravity caused by disformal coupling. Using a simple parametrization of the coupling function, in maximally disformal case, we constrain the model parameters by using the age constraints due to globular cluster data. We also obtain observational constraints on the parameters using [Formula: see text] datasets. In this case, we distinguish between phantom and non-phantom acceleration and show that the model can give rise to phantom behavior in a narrow region of parameter space.

scholarly journals Observational constraints on the generalized α attractor model

2018 ◽  
Vol 27 (05) ◽  
pp. 1850058 ◽  
Author(s):  
M. Shahalam ◽  
Ratbay Myrzakulov ◽  
Shynaray Myrzakul ◽  
Anzhong Wang
Keyword(s):  
Cosmic Acceleration ◽  
Asymptotic Region ◽  
Model Parameters ◽  
Observational Constraints ◽  
Late Time ◽  
Freezing And Thawing ◽  
Energy Models ◽  
Slow Roll ◽  
Attractor Model ◽  
Original Potential

We study the generalized [Formula: see text] attractor model in the context of the late time cosmic acceleration. The model interpolates between the scaling freezing and thawing dark energy models. In the slow roll region, the original potential is modified whereas the modification ceases in the asymptotic region and the effective potential behaves as the quadratic one. In our setting, the field rolls slowly around the present epoch and mimics the scaling behavior in the future. We obtain observational constraints on the model parameters by using an integrated database (SN+Hubble+BAO+CMB).

Constraints on kinematic model from Pantheon SNIa, OHD and CMB shift parameter measurements

2021 ◽  
Vol 36 (08) ◽  
pp. 2150049
Author(s):  
Abdulla Al Mamon
Keyword(s):  
Confidence Region ◽  
Kinematic Model ◽  
Hubble Constant ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Shift Parameter ◽  
Redshift Range ◽  
Data Points ◽  
Text Model ◽  
Good Agreement

In this paper, we reconstruct the late-time cosmological dynamics using a purely kinematic approach. In particular, considering a divergence-free parametrization for deceleration parameter [Formula: see text], we first derive the jerk parameter [Formula: see text] and then confront it with combination of various cosmological datasets. We use the most recent observational datasets consisting of the 1048 Pantheon Supernovae Ia data points in the redshift range [Formula: see text], the 51 data points of observational Hubble parameter (OHD) measurements in the redshift range [Formula: see text], the Hubble constant [Formula: see text] (R19) and the CMB shift parameter measurements. We study the evolution of different cosmological quantities for the present model and compare it with the concordance [Formula: see text]CDM model. We find that only the combined Pantheon+OHD+R19 data shows good agreement with the [Formula: see text]CDM [Formula: see text] model within [Formula: see text] confidence region. We also find that our model successfully generates late time cosmic acceleration along with a decelerated expansion in the past.

The nonlinear patterns of the cosmic anisotropy: the spatially flat perfect fluid universes.

2021 ◽  
Author(s):  
Leandro Gustavo Gomes
Keyword(s):  
Perfect Fluid ◽  
Hubble Parameter ◽  
Late Time ◽  
Algebraic Equations ◽  
Anisotropic Model ◽  
Bianchi Models ◽  
Principal Directions

Abstract In this manuscript, we investigate the patterns of the cosmological anisotropy in the spatially flat Bianchi models filled with a perfect fluid. We analyse the factor 1 + ∆R, the ratio of the Hubble parameter in the anisotropic model over its isotropic counterpart. In general, ∆R starts to deviate significantly from zero at a specific redshift zA, which depends on the type of the fluid and the value of the anisotropy magnitude. We also show that the deceleration and the jerk along the principal directions of the expansion tensor are constrained by simple algebraic equations that do not depend on the type of matter present. These characteristic patterns form a valuable framework to probe the cosmological anisotropy in the late-time universe.

scholarly journals A gravitational puzzle

2011 ◽  
Vol 369 (1957) ◽  
pp. 4998-5002
Author(s):  
Robert R. Caldwell
Keyword(s):  
Gravitational Lensing ◽  
Large Scale ◽  
Current Data ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Microwave Background ◽  
Scale Free ◽  
Cosmological Observations ◽  
Stress Energy ◽  
The Relationship

The challenge to understand the physical origin of the cosmic acceleration is framed as a problem of gravitation. Specifically, does the relationship between stress–energy and space–time curvature differ on large scales from the predictions of general relativity. In this article, we describe efforts to model and test a generalized relationship between the matter and the metric using cosmological observations. Late-time tracers of large-scale structure, including the cosmic microwave background, weak gravitational lensing, and clustering are shown to provide good tests of the proposed solution. Current data are very close to proving a critical test, leaving only a small window in parameter space in the case that the generalized relationship is scale free above galactic scales.

scholarly journals Anisotropic cosmological reconstruction in f(R, T) gravity

2018 ◽  
Vol 33 (29) ◽  
pp. 1850170 ◽  
Author(s):  
B. Mishra ◽  
Sankarsan Tarai ◽  
S. K. Tripathy
Keyword(s):  
Simple Approach ◽  
Cosmological Models ◽  
Gravity Theory ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Coupling Constant ◽  
Anisotropic Cosmological Models

Anisotropic cosmological models are constructed in f(R, T) gravity theory to investigate the dynamics of universe concerning the late time cosmic acceleration. Using a more general and simple approach, the effect of the coupling constant and anisotropy on the cosmic dynamics have been investigated. In this study, it is found that cosmic anisotropy substantially affects cosmic dynamics.

Sign in / Sign up

Export Citation Format

Share Document