scholarly journals Tachyon field as a dark energy in Bianchi type-V spacetime

2015 ◽  
Vol 30 (01) ◽  
pp. 1550008 ◽  
Author(s):  
J. Sadeghi ◽  
H. Farahani
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Bianchi Type ◽  
Scalar Potential ◽  
State Parameter ◽  
Tachyon Field ◽  
Equation Of State Parameter ◽  
Type V ◽  
Bianchi Type V

In this paper, we consider Bianchi type-V spacetime and study a cosmological model of dark energy based on tachyon scalar field. We assumed three different kinds of matter without possibility of interaction with scalar dark energy. Assuming power law Hubble parameter in terms of scale factor we obtain evolution of scalar field, scalar potential and equation of state parameter.

scholarly journals PHANTOM COSMOLOGY WITH A NONLINEAR BORN–INFELD TYPE SCALAR FIELD

2005 ◽  
Vol 14 (02) ◽  
pp. 355-362 ◽  
Author(s):  
H. Q. LU
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Energy Condition ◽  
State Parameter ◽  
Strong Energy Condition ◽  
Strong Energy ◽  
Accelerating Expansion ◽  
Equation Of State Parameter ◽  
The Universe

Recent many physicists suggest that the dark energy in the universe might result from the Born–Infeld (B–I) type scalar field of string theory. The universe of B–I type scalar field with potential can undergo a phase of accelerating expansion. The corresponding equation of state parameter lies in the range of -1<ω<-⅓. The equation of state parameter of B–I type scalar field without potential lies in the range of 0≤ω≤1. We find that weak energy condition and strong energy condition are violated for phantom B–I type scalar field. The equation of state parameter lies in the range of ω<-1.

scholarly journals DILATON COUPLED QUINTESSENCE MODEL IN THE ω - ω′ PLANE

2007 ◽  
Vol 16 (07) ◽  
pp. 1109-1117 ◽  
Author(s):  
Z. G. HUANG ◽  
H. Q. LU ◽  
W. FANG
Keyword(s):  
Dark Energy ◽  
Field Equation ◽  
Scalar Field ◽  
Equation Of State ◽  
State Parameter ◽  
Equation Of Motion ◽  
Gravitational Theory ◽  
Scalar Field Equation ◽  
Equation Of State Parameter ◽  
Quintessence Model

In this paper, we regard the dilaton in Weyl-scaled induced gravitational theory as a coupled quintessence. Based on this consideration, we investigate the dilaton coupled quintessence (DCQ) model in the ω - ω′ plane, which is defined by the equation of state parameter for the dark energy and its derivative with respect to N (the logarithm of the scale factor a). We find the scalar field equation of motion in the ω - ω′ plane, and show mathematically the properties of attractor solutions which correspond to ωσ ~ -1, ωσ = 1. Finally, we find that our model is a tracking one which belongs to "freezing" type models classified in the ω - ω′ plane.

Accreting Scalar-Field Models of Dark Energy Onto Morris-Thorne Wormhole

2016 ◽  
Vol 71 (10) ◽  
pp. 949-960
Author(s):  
Surajit Chattopadhyay ◽  
Antonio Pasqua ◽  
Irina Radinschi
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Power Law ◽  
State Parameter ◽  
Suitable Choice ◽  
Energy Models ◽  
Scalar Field Models ◽  
Equation Of State Parameter ◽  
Phantom Phase

AbstractThe present paper reports a study on accreting tachyon, Dirac-Born-Infeld essence and h-essence scalar field models of dark energy onto Morris-Thorne wormhole. Using three different parameterisation schemes and taking $H\, = \,{H_0}\, + \,{{{H_1}} \over t}$, we have derived the mass of the wormhole for all of the three parameterisation schemes that are able to get hold of both quintessence and phantom behaviour. With suitable choice of parameters, we observed that accreting scalar field dark energy models are increasing the mass of the wormhole in the phantom phase and the mass is decreasing in the quintessence phase. Finally, we have considered accretion with power law form of scale factor and without any parameterisation scheme for the equation of state parameter and observed the fact that phantom-type dark energy supports the existence of wormholes.

scholarly journals TACHYON FIELD-INSPIRED DARK ENERGY AND SUPERNOVAE CONSTRAINTS

2008 ◽  
Vol 17 (12) ◽  
pp. 2325-2335 ◽  
Author(s):  
JIE REN ◽  
XIN-HE MENG
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Hubble Parameter ◽  
Function Method ◽  
State Parameter ◽  
Data Sets ◽  
Tachyon Field ◽  
Shift Parameter ◽  
Energy Models ◽  
Equation Of State Parameter

The tachyon field in cosmology is studied in this paper by applying the generating function method to obtain exact solutions. The equation of state parameter of the tachyon field is [Formula: see text], which can be expressed as a function in terms of the redshift z. Based on these solutions, we propose some tachyon-inspired dark energy models to explore the properties of the corresponding cosmological evolution. The explicit relations between the Hubble parameter and redshift enable us to test the models with SNe Ia data sets easily. In this paper, we employ the SNe Ia data with the parameter [Formula: see text] measured from the SDSS and the shift parameter [Formula: see text] from WMAP observations to constrain the parameters in our models.

A new potential for scalar field dark energy

2020 ◽  
Vol 17 (09) ◽  
pp. 2050139
Author(s):  
Abdulla Al Mamon
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Hubble Parameter ◽  
Time Derivative ◽  
Field Potential ◽  
State Parameter ◽  
Simple Relation ◽  
Scale Factor ◽  
Equation Of State Parameter

In this paper, we have investigated some cosmological consequences of a quintessence dark energy model. In particular, we have obtained the forms of the equation of state parameter, the deceleration parameter and the field potential by considering a simple relation between the scale factor and the time derivative of the scalar field, instead of assuming any functional form for the scalar field potential or the scale factor or the equation of state parameter. We have found that the model provides the desired early deceleration followed by present acceleration of the universe. The potential derived numerically in this work in the form [Formula: see text], where [Formula: see text], [Formula: see text] and [Formula: see text] are real constant parameters. It has also been found that our model mimics as the standard [Formula: see text]CDM model in future. Finally, we have also shown the evolution of the normalized Hubble parameter for our model and the [Formula: see text]CDM model and compared that with the latest Hubble parameter data.

scholarly journals Twinlike models for parametrized dark energy

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
J. D. Dantas ◽  
J. J. Rodrigues
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Cosmic Time ◽  
State Parameter ◽  
Cosmological Models ◽  
Real Scalar ◽  
Flat Spacetime ◽  
Acceleration Parameter ◽  
Equation Of State Parameter

Abstract We study cosmological models involving a single real scalar field that has an equation of state parameter which evolves with cosmic time. We highlight some common parametrizations for the equation of state as a function of redshift in the context of twinlike theories. The procedure is used to introduce different models that have the same acceleration parameter, with the very same energy densities and pressure in flat spacetime.

scholarly journals QUINTESSENTIAL POWER-LAW COSMOLOGY: DARK ENERGY EQUATION OF STATE

2013 ◽  
Vol 28 (29) ◽  
pp. 1350122 ◽  
Author(s):  
BURIN GUMJUDPAI
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Power Law ◽  
Field Potential ◽  
State Parameter ◽  
Power Exponent ◽  
Acoustic Oscillations ◽  
Equation Of State Parameter ◽  
Canonical Scalar Field

Power-law cosmology with scale factor as power of cosmic time, a ∝tα, is investigated. We review and discuss value of α obtained from various types of observation. Considering dark energy dominant era in late universe from z < 0.5, we use observational derived results from Cosmic Microwave Background (CMB) (WMAP7), Baryon Acoustic Oscillations (BAOs) and observational Hubble data to find power exponent α and other cosmological variables. α is found to be 0.99 ±0.02 ( WMAP7 + BAO +H0) and 0.99 ±0.04 (WMAP7). These values do not exclude possibility of acceleration at 1σ hence giving viability to power-law cosmology in general. When considering scenario of canonical scalar field dark energy with power-law cosmology, we derive scalar field potential, exact scalar field solution and equation of state parameter. We found that the scenario of power-law cosmology containing dynamical canonical scalar field predicts present equation of state parameter wϕ, 0 = -0.449±0.030 while the w CDM with WMAP7 data (model independent, w constant) allows a maximum (+1σ) value of wϕ, 0 at -0.70 which is off the prediction range. However, in case of varying wϕ, the wϕ, 0 value predicted from quintessential power-law cosmology is allowed within 1σ uncertainty.

Interacting holographic dark energy in Bianchi type-V and IX universes with variable deceleration parameter

2020 ◽  
Vol 17 (10) ◽  
pp. 2050160
Author(s):  
H. Eser ◽  
C. B. Kilinc
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Deceleration Parameter ◽  
Bianchi Type ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Field Equations ◽  
Variable Deceleration Parameter ◽  
Type V ◽  
Bianchi Type V

In this paper, we study spatially homogeneous and anisotropic Bianchi type-V and IX universes filled with interacting dark matter and holographic dark energy. We obtained the solution of the field equations by using the variable deceleration parameter in the form [Formula: see text]. The cosmological parameters of the models like deceleration and equation of state are obtained. We observe that the deceleration parameter tends to [Formula: see text] which shows an accelerated universe, and the equation of state tends to [Formula: see text] which belongs to [Formula: see text]CDM model. Moreover, we establish the correspondence between holographic dark energy model and quintessence scalar field.

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