scholarly journals Late-Time Power-Law Stages of Cosmological Evolution in Teleparallel Gravity with Nonminimal Coupling

2017 ◽  
Vol 24 (1) ◽  
pp. 103-111 ◽  
Author(s):  
M. A. Skugoreva
Keyword(s):  
Power Law ◽  
Teleparallel Gravity ◽  
Cosmological Evolution ◽  
Late Time ◽  
Nonminimal Coupling

scholarly journals Intermediate Inflation or Late Time Acceleration?

2008 ◽  
Vol 2008 ◽  
pp. 1-16 ◽  
Author(s):  
Abhik Kumar Sanyal
Keyword(s):  
Scalar Field ◽  
Power Law ◽  
Cosmological Evolution ◽  
Expansion Rate ◽  
Accelerated Expansion ◽  
Kinetic Term ◽  
Late Time ◽  
Late Time Acceleration ◽  
Cosmic Evolution ◽  
Scaling Solution

The expansion rate of “intermediate inflation” lies between the exponential and power law expansion but corresponding accelerated expansion does not start at the onset of cosmological evolution. Present study of “intermediate inflation” reveals that it admits scaling solution and has got a natural exit form it at a later epoch of cosmic evolution, leading to late time acceleration. The corresponding scalar field responsible for such feature is also found to behave as a tracker field for gravity with canonical kinetic term.

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.

scholarly journals Unveiling the Evolution of Type I AGNs in the IR (15μm) — As Seen by ISO in the ELAIS-S1 Region

2002 ◽  
Vol 184 ◽  
pp. 167-172
Author(s):  
Israel Matute ◽  
Fabio La Franca ◽  
Carlotta Gruppioni ◽  
Francesca Pozzi ◽  
Carlo Lari
Keyword(s):  
Power Law ◽  
Luminosity Function ◽  
Evolution Model ◽  
Cosmological Evolution ◽  
Type I ◽  
Infrared Background ◽  
Power Law Function ◽  
Cosmic Infrared Background ◽  
Luminosity Evolution

AbstractWe present the first estimate of the evolution of type 1 AGNs in the IR (15 μm) obtained from the ELAIS survey in the S1 region. We find that the luminosity function (LF) of Type 1 AGNs at 15μm is fairly well represented by a double power-law function with a bright slope of 2.9 and a faint slope of 1.1. There is evidence for significant cosmological evolution according to a pure luminosity evolution model L15(z)α(l+z)k, with in a (Ωm,ΩΛ)=(1.0,0.0) cosmology. This evolution is similar to what is observed at other wavebands. From the luminosity function and its evolution, we estimate a contribution of ~ 2% from Type 1 AGN to the total Cosmic Infrared Background (CIRB) at 15 μm.

Dynamical system approach to cosmological evolution in modified theories of gravity with coupling between matter and geometry

2020 ◽  
Vol 35 (19) ◽  
pp. 2050154
Author(s):  
Jun Wang ◽  
Kang Liu
Keyword(s):  
Dynamical System ◽  
System Approach ◽  
Cosmic Radiation ◽  
Cosmological Evolution ◽  
Accelerated Expansion ◽  
Modified Theories Of Gravity ◽  
Late Time ◽  
Dynamical System Approach ◽  
Dynamical Approach ◽  
Theories Of Gravity

In this paper, a class of [Formula: see text] gravitational models with coupling between matter and geometry have been studied by a dynamical approach in cosmology. The result shows that both the cosmic radiation dominated era and the late-time cosmic accelerated expansion can be achieved in this class of models. Moreover, the corresponding parameters are constrained as well.

Analysis of observational parameters and stability in extended teleparallel gravity

2020 ◽  
Vol 17 (11) ◽  
pp. 2050158
Author(s):  
A. Y. Shaikh ◽  
B. Mishra
Keyword(s):  
Thermodynamic Temperature ◽  
Teleparallel Gravity ◽  
Entropy Density ◽  
Accelerated Expansion ◽  
Late Time ◽  
General Relativistic ◽  
Basic Equations ◽  
The Stability ◽  
The Universe ◽  
Early Phases

In this paper, we have investigated the stability of General Relativistic Hydrodynamics (GRHD) model in a Friedmann–Robertson–Walker space-time with the volumetric power law in teleparallel gravity. The basic equations are derived along with its thermodynamical aspects. Thermodynamic temperature and entropy density of the model are also obtained. The state finder diagnostic pair and jerk parameter are analyzed to characterize different phases of the universe and the well-known astrophysical phenomena such as look-back time, the luminosity distance with redshift are derived. The model shows an accelerated expansion with inflationary era in the early and the very late time of the cosmic evolution. The GRHD model is stable at the early phases of the universe and is unstable at late times.

scholarly journals Effect of Fast Scale Factor Fluctuations on Cosmological Evolution

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 164
Author(s):  
Igor I. Smolyaninov
Keyword(s):  
Quantum Fluctuations ◽  
Scale Factor ◽  
Cosmological Evolution ◽  
Accelerated Expansion ◽  
Late Time ◽  
Cosmological Constant Problem ◽  
Friedmann Equations ◽  
Newtonian Dynamics ◽  
Expansion Of The Universe ◽  
The Universe

In this paper, we study the corrections to the Friedmann equations due to fast fluctuations in the universe scale factor. Such fast quantum fluctuations were recently proposed as a potential solution to the cosmological constant problem. They also induce strong changes to the current sign and magnitude of the average cosmological force, thus making them one of the potential probable causes of the modification of Newtonian dynamics in galaxy-scale systems. It appears that quantum fluctuations in the scale factor also modify the Friedmann equations, leading to a considerable modification of cosmological evolution. In particular, they give rise to the late-time accelerated expansion of the universe, and they may also considerably modify the effective universe potential.

Dynamical properties of scaling solutions in teleparallel dark energy cosmologies with nonminimal coupling

2017 ◽  
Vol 26 (09) ◽  
pp. 1750103 ◽  
Author(s):  
Mihai Marciu
Keyword(s):  
Dark Energy ◽  
Power Law ◽  
Scalar Fields ◽  
Teleparallel Gravity ◽  
Inverse Power ◽  
Coupling Coefficients ◽  
Potential Term ◽  
Inverse Power Law ◽  
The Stability ◽  
The Impact

The dynamical aspects of scaling solutions for the dark energy component in the theoretical framework of teleparallel gravity are considered, where dark energy is represented by a scalar field nonminimally coupled with the torsion and with a boundary term, where the boundary coupling term represents the divergence of the torsion vector. The behavior and stability of the scaling solutions are studied for scalar fields endowed with inverse power law potentials and with exponential potentials. It is shown that for scalar fields endowed with inverse power-law potentials, the stability conditions are not affected by the coupling coefficients. For the scalar fields endowed with exponential potentials, two cases are studied: at first, we have considered an infinitesimal deviation from the scaling solution in the corresponding Klein–Gordon equation, and the impact of distinct coupling coefficients on the stability of the solution are analyzed. Secondly, the potential-free case is considered where the dominance of the coupling terms over the potential term is analyzed, discussing the validity of the corresponding particular solution.

scholarly journals A novel teleparallel dark energy model

2016 ◽  
Vol 25 (02) ◽  
pp. 1650025 ◽  
Author(s):  
Giovanni Otalora
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Teleparallel Gravity ◽  
Accelerated Expansion ◽  
Late Time ◽  
De Sitter ◽  
Sitter Group ◽  
Current State ◽  
Expansion Of The Universe ◽  
The Universe

Although equivalent to general relativity, teleparallel gravity (TG) is conceptually speaking a completely different theory. In this theory, the gravitational field is described by torsion, not by curvature. By working in this context, a new model is proposed in which the four-derivative of a canonical scalar field representing dark energy is nonminimally coupled to the “vector torsion”. This type of coupling is motivated by the fact that a scalar field couples to torsion through its four-derivative, which is consistent with local spacetime kinematics regulated by the de Sitter group [Formula: see text]. It is found that the current state of accelerated expansion of the universe corresponds to a late-time attractor that can be (i) a dark energy-dominated de Sitter solution ([Formula: see text]), (ii) a quintessence-type solution with [Formula: see text], or (iii) a phantom-type [Formula: see text] dark energy.

scholarly journals Viscous coupled fluids in terms of a log-corrected equation-of-state

2021 ◽  
Vol 18 (12) ◽  
Author(s):  
I. Brevik ◽  
K. Myrzakulov ◽  
A. V. Timoshkin ◽  
A. Zhadyranova
Keyword(s):  
Dark Matter ◽  
Comparative Analysis ◽  
Equation Of State ◽  
Energy Density ◽  
Power Law ◽  
Late Time ◽  
System Of Equations ◽  
Power Law Fluid ◽  
Power Law Equation ◽  
Detailed Picture

In this paper, we consider a class of cosmological fluids that possess properties analogous to those of crystalline solids undergoing isotropic deformations. Our research is based on a modified log-corrected power-law equation of state in the presence of a bulk viscosity. This formalism represents a class of the so-called logotropic fluids, and allows explaining an accelerating late-time universe. In order to obtain a more detailed picture of its evolution, we add in our model a coupling of the log-corrected power-law fluid to dark matter, and study various interacting forms between them. We solve the system of equations for a modified log-power-law fluid coupled to dark matter, and obtain expressions for the log-corrected power-law energy density, and the energy density for dark matter. A comparative analysis is made with the model of a nonviscous log-corrected power-law fluid without interaction with dark matter.

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