A probe of cosmological models in modified teleparallel gravity

2021 ◽  
pp. 2150208
Author(s):  
Archana Dixit ◽  
Anirudh Pradhan ◽  
Dinesh Chandra Maurya
Keyword(s):  
Hubble Constant ◽  
Teleparallel Gravity ◽  
Cosmological Term ◽  
Cosmological Models ◽  
Model Parameters ◽  
Late Time ◽  
General Function ◽  
Eos Parameter ◽  
Variable Cosmological Term ◽  
Present Universe

In this paper, we have investigated the physical behavior of cosmological models in modified Teleparallel gravity with a general function [Formula: see text] where [Formula: see text] and [Formula: see text] are model parameters and [Formula: see text] is the torsion scalar. We have considered a homogeneous and isotropic Friedman universe filled with perfect fluid. We have derived the deceleration parameter [Formula: see text] in terms of equation of state (EoS) parameter [Formula: see text] and Hubble parameter [Formula: see text]. We have investigated the variation of [Formula: see text] over the observed values of Hubble constant in various observations within the range of redshift [Formula: see text]. Also, we have studied effective energy density [Formula: see text], effective pressure [Formula: see text] and effective EoS parameter [Formula: see text]. We have observed that the second term of [Formula: see text] function behaves just like variable cosmological term [Formula: see text] ([Formula: see text]) at late-time universe and causes the acceleration in expansion and works just like dark energy candidates. Also, we have evaluated the age of the present universe for various stages of matter [Formula: see text] and various [Formula: see text] functions.

Cosmological models in R2 gravity with hybrid expansion law

2021 ◽  
pp. 2150143
Author(s):  
Partha Sarathi Debnath ◽  
Bikash Chandra Paul
Keyword(s):  
Equation Of State ◽  
Deceleration Parameter ◽  
State Parameter ◽  
Cosmological Models ◽  
Model Parameters ◽  
Density Parameter ◽  
Eos Parameter ◽  
Data Set ◽  
Deceleration Phase ◽  
Higher Derivative

In this paper, evolution of a Friedmann–Robertson–Walker universe is studied in a higher derivative theory of gravity. The relativistic solutions admitting hybrid expansion law of the universe are explored here. Hybrid expansion law is a general form of scale factor from which one can recover both the power-law expansion and exponential expansion as a special case. The hybrid expansion law is interesting as it addresses the early deceleration phase and presents accelerating phase satisfactorily. It is found that an inflationary scenario with hybrid expansion law is permitted in the [Formula: see text] gravity fairly well. We consider universe filled with cosmic fluid that describes by an equation of state (EoS) parameter which varies with time. Consequently, we analyze the time variation of energy density parameter, cosmic pressure, equation of state parameter, deceleration parameter and jerk parameter in the cosmological model. The constraints of the model parameters imposed by the cosmological observational data set are determined. The present value of the deceleration parameter [Formula: see text], EoS parameter and the epoch at which the transition of decelerated phase to accelerated phase are estimated. In the higher derivative theory, we obtain some new and interesting cosmological solutions relevant for building cosmological models.

scholarly journals Cosmological models with a hybrid scale factor

2021 ◽  
pp. 2140005
Author(s):  
S. K. Tripathy ◽  
B. Mishra ◽  
Maxim Khlopov ◽  
Saibal Ray
Keyword(s):  
General Relativity ◽  
Scale Factor ◽  
Cosmological Models ◽  
Late Time ◽  
Late Time Acceleration ◽  
Present Universe ◽  
Matter Fields

In this paper, we present some cosmological models with a hybrid scale factor (HSF) in the framework of general relativity (GR). The HSF fosters an early deceleration as well as a late-time acceleration and mimics the present Universe. The dynamical aspects of different cosmological models with HSF in the presence of different matter fields have been discussed.

ASYMPTOTIC BEHAVIOR OF HOMOGENEOUS COSMOLOGICAL MODELS ON THE BRANE

2003 ◽  
Vol 18 (17) ◽  
pp. 1197-1203
Author(s):  
SUBENOY CHAKRABORTY
Keyword(s):  
Cosmological Term ◽  
Cosmological Models ◽  
Brane World ◽  
Late Time ◽  
Time Behavior ◽  
De Sitter ◽  
Bianchi Models ◽  
Bianchi Ix ◽  
Homogeneous Cosmological Models ◽  
Matter Fields

In this work, we have studied the late-time behavior of initially expanding homogeneous cosmological models with a positive cosmological term in Randall–Sundrum brane-world type scenarios. The matter fields are confined in the three-brane, onto which the five-dimensional Weyl tensor has a nonvanishing projection. It is found that all Bianchi models (except IX) exponentially evolve toward the de Sitter solution while the Bianchi IX model also isotropizes but with a restriction on the cosmological parameter.

scholarly journals Cosmological models, observational data and tension in Hubble constant

2020 ◽  
pp. 1-20
Author(s):  
G.S. Sharov ◽  
E.S. Sinyakov
Keyword(s):  
Observational Data ◽  
Hubble Parameter ◽  
Background Radiation ◽  
Hubble Constant ◽  
Cosmological Models ◽  
Model Parameters ◽  
Data Sets ◽  
Type Ia ◽  
Data Points ◽  
Ia Supernovae

We analyze how predictions of cosmological models depend on a choice of described observational data, restrictions on flatness, and how this choice can alleviate the H tension. These effects are demonstrated in the wCDM model in comparison with the standard ΛCDM model. We describe the Pantheon sample observations of Type Ia supernovae, 31 Hubble parameter data points H(z) from cosmic chronometers, the extended sample with 57 H(z) data points and observational manifestations of cosmic microwave background radiation (CMB). For the wCDM and ΛCDM models in the flat case and with spatial curvature, we calculate χfunctions for all observed data in different combinations, estimate optimal values of model parameters and their expected intervals. For both considered models the results essentially depend on a choice of data sets. In particular, for the wCDM model with H(z) data, supernovae and CMB the 1σ estimations may vary from H = 67.52km /(s·Mpc) (for all N = 57 Hubble parameter data points) up to H = 70.87 /(s·Mpc) for the flat case (k = 0) and N = 31. These results might be a hint how to alleviate the problem of H tension: different estimates of the Hubble constant may be connected with filters and a choice of observational data.

scholarly journals Interacting Rényi holographic dark energy with parametrization on the interaction term

2021 ◽  
Author(s):  
Umesh Kumar Sharma ◽  
Vipin Chandra Dubey
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Model Parameters ◽  
Density Parameter ◽  
Late Time ◽  
Frw Universe ◽  
Eos Parameter ◽  
Interaction Term

In this work, we study the Rényi holographic dark energy (RHDE) model in a flat FRW Universe where the infrared cut-off is taken care by the Hubble horizon and also by taking three different parametrizations of the interaction term between the dark matter and the dark energy. Analyzing graphically, the behavior of some cosmological parameters in particular deceleration parameter, equation of state (EoS) parameter, energy density parameter and squared speed of sound, in the process of the cosmic evolution, is found to be leading towards the late-time accelerated expansion of the RHDE model. Also, we find the departure for the derived models from the standard [Formula: see text]CDM model according to the evolution of jerk parameter. Moreover, we compare the model parameters by considering the observational Hubble data which consist of 51 points in the redshift range [Formula: see text].

Perfect fluid Bianchi type-I cosmological models with time-dependent cosmological term Λ

2018 ◽  
Vol 15 (08) ◽  
pp. 1850132
Author(s):  
J. P. Singh ◽  
Prashant S. Baghel ◽  
Abhay Singh
Keyword(s):  
Perfect Fluid ◽  
Bianchi Type ◽  
Cosmological Term ◽  
Cosmological Models ◽  
Time Dependent ◽  
Late Time ◽  
Type I ◽  
Field Equations ◽  
Vacuum Decay ◽  
Bianchi Type I

We present perfect fluid Bianchi type-I cosmological models with time-dependent cosmological term [Formula: see text]. Exact solutions of the Einstein’s field equations are presented via a suitable functional form for Hubble parameter [Formula: see text], which yields a model of the universe that represents initially decelerating and late-time accelerating expansion. We discuss, in the context of some vacuum decay laws, cosmological implications of the corresponding solutions. The physical and geometrical features of the models are also discussed.

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