scholarly journals Accelerating universe in modified teleparallel gravity theory

2019 ◽  
Vol 15 (S356) ◽  
pp. 397-399
Author(s):  
Shambel Sahlu ◽  
Joseph Ntahompagaze ◽  
Amare Abebe ◽  
David F. Mota
Keyword(s):  
State Parameter ◽  
Teleparallel Gravity ◽  
Gravity Theory ◽  
Gravity Models ◽  
Accelerating Universe ◽  
Late Time ◽  
Numerical Result ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

AbstractThis paper studies the cosmology of accelerating expansion of the universe in modified teleparallel gravity theory. We discuss the cosmology of f(T, B) gravity theory and its implication to the new general form of the equation of state parameter wTB for explaining the late-time accelerating expansion of the universe without the need for the cosmological constant scenario. We examine the numerical value of wTB in different paradigmatic f(T, B) gravity models. In those models, the numerical result of wTB is favored with observations in the presence of the torsion scalar T associated with a boundary term B and shows the accelerating expansion of the universe.

scholarly journals THE EVOLUTION OF THE UNIVERSE WITH THE B–I TYPE PHANTOM SCALAR FIELD

2006 ◽  
Vol 15 (02) ◽  
pp. 199-214 ◽  
Author(s):  
WEI FANG ◽  
H. Q. LU ◽  
Z. G. HUANG ◽  
K. F. ZHANG
Keyword(s):  
Scalar Field ◽  
State Parameter ◽  
Phase Plane Analysis ◽  
Density Parameter ◽  
Late Time ◽  
Plane Analysis ◽  
Accelerating Expansion ◽  
Phantom Scalar ◽  
Expansion Of The Universe ◽  
The Universe

We consider the phantom cosmology with a Lagrangian [Formula: see text] originated from the nonlinear Born–Infeld type scalar field. This cosmological model can explain the accelerating expansion of the universe with the equation of state parameter w ≤ -1. We get a sufficient condition for an arbitrary potential that admits a late time attractor solution: the value of potential u(Xc) at the critical point (Xc, 0) should be maximum and greater than zero. We study a specific potential with the form of [Formula: see text] via phase plane analysis and compute the cosmological evolution by numerical analysis in detail. The results show that the phantom field survives till today (to account for the present observed accelerating expansion) without interfering with the nucleosynthesis of the standard model (the density parameter Ωϕ≃10-12 at the equipartition epoch), and also avoid the future collapse of the universe.

scholarly journals Almost-Pseudo-Ricci Symmetric FRW Universe with a Dynamic Cosmological Term and Equation of State

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 205
Author(s):  
Sanjay Mandal ◽  
Avik De ◽  
Tee-How Loo ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Equation Of State ◽  
Cosmological Parameters ◽  
Cosmological Term ◽  
Ricci Scalar ◽  
Energy Conditions ◽  
Late Time ◽  
Frw Universe ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

The objective of the present paper is to investigate an almost-pseudo-Ricci symmetric FRW spacetime with a constant Ricci scalar in a dynamic cosmological term Λ(t) and equation of state (EoS) ω(t) scenario. Several cosmological parameters are calculated in this setting and thoroughly studied, which shows that the model satisfies the late-time accelerating expansion of the universe. We also examine all of the energy conditions to check our model’s self-stability.

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.

Swampland criteria and cosmological behavior of Tsallis holographic dark energy in Bianchi -III Universe

2020 ◽  
Vol 17 (07) ◽  
pp. 2050098 ◽  
Author(s):  
Umesh Kumar Sharma ◽  
Shikha Srivastava ◽  
A. Beesham
Keyword(s):  
Dark Energy ◽  
Deceleration Parameter ◽  
Holographic Dark Energy ◽  
Accelerating Universe ◽  
Accelerating Expansion ◽  
Bianchi Iii ◽  
Expansion Of The Universe ◽  
Hubble Horizon ◽  
The Universe ◽  
Universe Evolution

In this paper, a new form of dark energy, known as Tsallis holographic dark energy (THDE), with IR cutoff as Hubble horizon proposed by Tavayef et al. Tsallis holographic dark energy, Phys. Lett. B 781 (2018) 195 has been explored in Bianchi-III model with the matter. By taking the time subordinate deceleration parameter, the solution of Einstein’s field equation is found. The Universe evolution from earlier decelerated to the current accelerated phase is exhibited by the deceleration parameter acquired in the THDE model. It can be seen that the derived THDE model is related to an accelerating Universe with quintessence ([Formula: see text]). The squared sound speed [Formula: see text] also suggests that the THDE model is classically stable at present. In addition, the quintessence phase of the THDE model is analyzed with swampland conjecture to reformulate the accelerating expansion of the Universe.

scholarly journals Dynamical Properties of Dark Energy Models in Fractal Universe

Symmetry ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1174
Author(s):  
Muhammad Umair Shahzad ◽  
Ayesha Iqbal ◽  
Abdul Jawad
Keyword(s):  
Dark Energy ◽  
State Parameter ◽  
Accelerated Expansion ◽  
Accelerating Universe ◽  
Statefinder Parameters ◽  
Om Diagnostic ◽  
Energy Models ◽  
Expansion Of The Universe ◽  
Dynamical Properties ◽  
The Universe

In this paper, we consider the flat FRW spacetime filled with interacting dark energy and dark matter in fractal universe. We work with the three models of dark energy named as Tsallis, Renyi and Sharma–Mittal. We investigate different cosmological implications such as equation of state parameter, squared speed of sound, deceleration parameter, statefinder parameters, ω e f f - ω e f f ´ (where prime indicates the derivative with respect to ln a , and a is cosmic scale factor) plane and Om diagnostic. We explore these parameters graphically to study the evolving universe. We compare the consistency of dark energy models with the accelerating universe observational data. All three models are stable in fractal universe and support accelerated expansion of the universe.

scholarly journals VISCOUS DARK ENERGY IN f(T) GRAVITY

2013 ◽  
Vol 28 (27) ◽  
pp. 1350118 ◽  
Author(s):  
M. SHARIF ◽  
SHAMAILA RANI
Keyword(s):  
Dark Energy ◽  
Graphical Representation ◽  
Teleparallel Gravity ◽  
Eos Parameter ◽  
Phantom Divide ◽  
Accelerating Expansion ◽  
Phantom Divide Line ◽  
Expansion Of The Universe ◽  
Crossing Of Phantom Divide ◽  
The Universe

We study the bulk viscosity taking dust matter in the generalized teleparallel gravity. We consider different dark energy (DE) models in this scenario along with a time-dependent viscous model to construct the viscous equation of state (EoS) parameter for these DE models. We discuss the graphical representation of this parameter to investigate the viscosity effects on the accelerating expansion of the universe. It is mentioned here that the behavior of the universe depends upon the viscous coefficients showing the transition from decelerating to accelerating phase. It leads to the crossing of phantom divide line and becomes phantom dominated for specific ranges of these coefficients.

scholarly journals ADDRESSING THE CRISIS IN FUNDAMENTAL PHYSICS

2007 ◽  
Vol 16 (12a) ◽  
pp. 1947-1952
Author(s):  
CHRISTOPHER W. STUBBS
Keyword(s):  
Dark Energy ◽  
State Parameter ◽  
New Physics ◽  
Fundamental Physics ◽  
Accelerating Expansion ◽  
Cosmological Observations ◽  
Real Risk ◽  
Expansion Of The Universe ◽  
The One ◽  
The Universe

The observation that the expansion of the Universe is proceeding at an ever-increasing rate, i.e. the "dark energy" problem, constitutes a crisis in fundamental physics that is as profound as the one that preceded the advent of quantum mechanics. Cosmological observations currently favor a dark energy equation-of-state parameter w = P/ρ = -1. Awkwardly, this is the value that has the least ability to discriminate between alternatives for the physics that produces the observed accelerating expansion. If this result persists we therefore run a very real risk of stagnation in our attempt to better understand the nature of this new physics, unless we uncover another piece of the dark energy puzzle. I argue that precision fundamental measurements in space have an important role in addressing this crisis.

scholarly journals Updated f(T) gravity constraints from high-redshift cosmography

2015 ◽  
Vol 24 (14) ◽  
pp. 1550100 ◽  
Author(s):  
Ester Piedipalumbo ◽  
Enrica Della Moglie ◽  
Roberto Cianci
Keyword(s):  
Gamma Ray ◽  
Probability Distributions ◽  
High Redshift ◽  
Teleparallel Gravity ◽  
Gravity Theory ◽  
Gravity Models ◽  
Acoustic Oscillations ◽  
Dynamical Equations ◽  
Data Set ◽  
The Universe

In the last dozen years, a wide and variegated mass of observational data revealed that the universe is now expanding at an accelerated rate. In the absence of a well-based theory to interpret the observations, cosmography provides information about the evolution of the universe from measured distances, only assuming that the geometry can be described by the Friedmann–Lemaitre–Robertson–Walker metric. In this paper, we perform a high-redshift analysis which allows us to put constraints on the cosmographic parameters up to the fifth-order, thus inducing indirect constraints on any gravity theory. Here, we are interested in the so-called teleparallel gravity theory, [Formula: see text]. Actually, we use the analytical expressions of the present day values of [Formula: see text] and its derivatives as functions of the cosmographic parameters to map the cosmography region of confidences into confidence ranges for [Formula: see text] and its derivative. Moreover, we show how these can be used to test some teleparallel gravity models without solving the dynamical equations. Our analysis is based on the Union2 Type Ia supernovae (SNIa) data set, a set of 28 measurements of the Hubble parameter, the Hubble diagram constructed from some gamma ray bursts (GRB) luminosity distance indicators and Gaussian priors on the distance from the baryon acoustic oscillations (BAOs) and the Hubble constant [Formula: see text]. To perform our statistical analysis and to explore the probability distributions of the cosmographic parameters, we use the Markov chain Monte Carlo (MCMC) method.

scholarly journals Noether symmetry approach in f (T, B) teleparallel gravity with a fermionic field

2021 ◽  
Vol 2090 (1) ◽  
pp. 012058
Author(s):  
Yerlan Myrzakulov ◽  
Sabit Bekov ◽  
Kairat Myrzakulov
Keyword(s):  
Cosmological Model ◽  
Teleparallel Gravity ◽  
Noether Symmetry ◽  
Accelerated Expansion ◽  
Late Time ◽  
Fermionic Field ◽  
Symmetry Approach ◽  
Expansion Of The Universe ◽  
Isotropic Cosmological Model ◽  
The Universe

Abstract In this work, we consider a homogeneous and isotropic cosmological model of the universe in f (T, B) gravity with non-minimally coupled fermionic field. In order to find the form of the coupling function F(Ψ), the potential function V (Ψ) of the fermionic field and the function f (T, B), we found through the Noether symmetry approach. The results obtain are coincide with the observational data that describe the late-time accelerated expansion of the universe.

Built-in inflation in f(G) gravity

2016 ◽  
Vol 25 (01) ◽  
pp. 1650011 ◽  
Author(s):  
M. Sharif ◽  
H. Ismat Fatima
Keyword(s):  
Energy Density ◽  
Late Time ◽  
Universe Model ◽  
Frw Universe ◽  
Eos Parameter ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Bonnet Term

In this paper, we study the role of Gauss–Bonnet term for the early and late time accelerating phases of the universe with the help of two viable [Formula: see text] models in the background of flat FRW universe model. These models show inflationary behavior as well as the present accelerating expansion of the universe. The contribution of Gauss–Bonnet term in pressure and energy density is used to calculate equation of state (EoS) parameter for the modified fluid which behaves like cosmological constant with [Formula: see text]. We discuss early inflation and late accelerating expansion of the universe through scale factor evaluated from equation of continuity numerically.

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