Thermodynamics in loop quantum cosmology with non-canonical scalar field model

2019 ◽  
Vol 16 (06) ◽  
pp. 1950081
Author(s):  
Ayesha Iqbal ◽  
Abdul Jawad
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
Equilibrium Condition ◽  
Field Model ◽  
State Parameter ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Generalized Second Law ◽  
Equation Of State Parameter ◽  
The Universe

The cosmological scenario is built up within the framework of scalar field model possessing a noncanonical kinetic term in loop quantum gravity. The noncanonical scalar field is permitted to interact with dark matter field by assuming a specific form of coupling term. The equation of state parameter is set to be constant as well as variable (Chevallier–Polarski–Linder parametrization) and evaluated the behavior of universe through deceleration parameter and weak energy condition. These parameters favor the accelerated expansion of the universe for three values of equation of state parameter in both cases allowed by observational data. The squared speed of sound leads to the stability of the underlying models in both forms of equation of state parameter. Moreover, the validity of generalized second law of thermodynamics is analyzed by using first law of thermodynamics and assume the universe to be enclosed by apparent horizon. The Bekenstein, logarithmic and power-law entropy is being considered as entropy of horizon. The thermodynamic equilibrium condition is also discussed for all three cases of entropies. The generalized second law of thermodynamics and thermal equilibrium condition is satisfied for all the three types of entropies.

Cosmological consequences of modified Friedmann equations according to holographic equipartition law

2021 ◽  
Vol 36 (10) ◽  
pp. 2150069
Author(s):  
Abdul Jawad ◽  
Sidra Saleem ◽  
Saba Qummer
Keyword(s):  
Equation Of State ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Om Diagnostic ◽  
Generalized Second Law ◽  
Friedmann Equations ◽  
Equation Of State Parameter ◽  
Equipartition Law

We examine thermodynamically an extra driving term for the flat universe by applying Sharma Mittal entropy to Padmanabhan’s holographic equipartition law. Deviations from the Bekenstein–Hawking entropy by using this law, we generate an extra driving in the acceleration equation. By using the constant and parametrized equation of state parameter, we investigate the different cosmological parameters like deceleration parameter, squared speed of sound, Om-diagnostic and statefinder parameter through graphical approach. We observe compatible results with current observational data in both models. Generalized second law of thermodynamics also remains valid in both cases.

Cosmological consequences and thermodynamics of modified gravity with extended nonminimal derivative couplings

2019 ◽  
Vol 28 (11) ◽  
pp. 1950137 ◽  
Author(s):  
Abdul Jawad ◽  
M. Bilal Amin ◽  
Shamaila Rani
Keyword(s):  
Equation Of State ◽  
Speed Of Sound ◽  
State Parameter ◽  
Second Law Of Thermodynamics ◽  
Frw Universe ◽  
Generalized Second Law ◽  
Horizon Entropy ◽  
Equation Of State Parameter ◽  
The Stability ◽  
The Universe

We consider the newly proposed gravitational modifications that go beyond Horndeski’s theory, named as theories with extended nonminimal derivative couplings. By these modifications, the coefficient functions depend on the scalar field and its kinetic energy. These theories become ghost-free in cosmological background. We consider the flat FRW universe and explore the equation-of-state parameter, [Formula: see text]–[Formula: see text] plane and the squared speed of sound. The equation-of-state parameter exhibits phantom behavior of the universe, [Formula: see text]–[Formula: see text] plane represents the freezing region of the universe while the squared speed of sound denotes the stability of the model for the specific choice of constant parameters. Also, we investigate the validity of generalized second law of thermodynamics on the Hubble horizon taking into account the Bekenstein, power-law, Renyi and logarithmic corrections to the horizon entropy.

scholarly journals Chameleon field dynamics during inflation

2018 ◽  
Vol 27 (04) ◽  
pp. 1850041 ◽  
Author(s):  
Nasim Saba ◽  
Mehrdad Farhoudi
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
State Parameter ◽  
Big Bang ◽  
Late Time ◽  
Inflationary Model ◽  
Slow Roll ◽  
Equation Of State Parameter ◽  
The Common ◽  
The Universe

By studying the chameleon model during inflation, we investigate whether it can be a successful inflationary model, wherein we employ the common typical potential usually used in the literature. Thus, in the context of the slow-roll approximations, we obtain the e-folding number for the model to verify the ability of resolving the problems of standard big bang cosmology. Meanwhile, we apply the constraints on the form of the chosen potential and also on the equation of state parameter coupled to the scalar field. However, the results of the present analysis show that there is not much chance of having the chameleonic inflation. Hence, we suggest that if through some mechanism the chameleon model can be reduced to the standard inflationary model, then it may cover the whole era of the universe from the inflation up to the late time.

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 ENTROPY OF COSMOLOGICAL BLACK HOLES AND THE GENERALIZED SECOND LAW IN THE PHANTOM-ENERGY-DOMINATED UNIVERSE

2011 ◽  
Vol 20 (02) ◽  
pp. 233-252 ◽  
Author(s):  
KHIREDDINE NOUICER
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Equation Of State ◽  
State Parameter ◽  
Phantom Energy ◽  
Energy Conditions ◽  
Second Law ◽  
Brick Wall ◽  
Generalized Second Law ◽  
Equation Of State Parameter

Adopting the thin layer improved brick wall method, we investigate the thermodynamics of a black hole embedded in a spatially flat Friedmann–Robertson–Walker universe. We calculate the temperature and the entropy at every apparent horizon for arbitrary solution of the scale factor. We show that the temperature and entropy display a nontrivial behavior as functions of time. In the case of black holes immersed in a universe driven by phantom energy, we show that for specific ranges of the equation-of-state parameter and apparent horizons the entropy is compatible with the D-bound conjecture, and even the null, dominant and strong energy conditions are violated. In the case of accretion of phantom energy onto a black hole with small Hawking–Hayward quasi-local mass, we obtain an equation-of-state parameter in the range w ≤ -5/3, guaranteeing the validity of the generalized second law.

scholarly journals A COMPARISON OF QUINTESSENCE AND NON-LINEAR BORN–INFELD SCALAR FIELD USING GOLD SUPERNOVA DATA

2006 ◽  
Vol 15 (11) ◽  
pp. 1947-1961 ◽  
Author(s):  
WEI FANG ◽  
H. Q. LU ◽  
B. LI ◽  
K. F. ZHANG
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
Field Model ◽  
State Parameter ◽  
Scale Factor ◽  
Scalar Field Model ◽  
Equation Of State Parameter ◽  
Non Linear ◽  
Quintessence Model

We study the Non-Linear Born–Infeld (NLBI) scalar field model and quintessence model with two different potentials (V(ϕ) = -sϕ and [Formula: see text]). We investigate the differences between these two models. We explore the equation of state parameter w and the evolution of scale factor a(t) in both the NLBI scalar field and quintessence model. The present age of universe and the transition redshift are also obtained. We use the Gold dataset of 157 SN-Ia to constrain the parameters of the two models. All the results show that the NLBI model is slightly superior to the quintessence model.

Reconstruction of f(T) gravity in the context of standard Chaplygin gas as tachyon scalar field and study of the stability against gravitational perturbation

2019 ◽  
Vol 16 (07) ◽  
pp. 1950101
Author(s):  
Surajit Chattopadhyay ◽  
Soumyodipta Karmakar
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
State Parameter ◽  
Chaplygin Gas ◽  
Gravitational Perturbation ◽  
Gravitational Perturbations ◽  
Equation Of State Parameter ◽  
Speed Parameter ◽  
The Stability ◽  
The Universe

The present paper reports a study on the [Formula: see text] gravity reconstruction scheme in the context of considering standard Chaplygin gas as tachyon scalar field model of dark energy. The solution for reconstructed [Formula: see text] gravity has been obtained from reconstructed potential and scalar field of tachyon based on the standard Chaplygin gas. It has been observed that the equation of state parameter due to the reconstructed torsion contribution to the density and pressure behaves like quintom and is consistent with the observational value of the equation of state parameter for the current universe. The reconstructed [Formula: see text] has then been tested for gravitational perturbation by deriving the frictional term, the effective mass and the sound speed parameter for the gravitational potential and it has been found to be stable against gravitational perturbations through positive value of the squared speed of sound. Finally, statefinder diagnostics has been carried out and the reconstructed [Formula: see text] gravity is found to interpolate between dust and [Formula: see text]CDM phases of the universe.

scholarly journals Thawing and freezing quintessence models: a thermodynamic consideration

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Tanima Duary ◽  
Ananda Dasgupta ◽  
Narayan Banerjee
Keyword(s):  
Scalar Field ◽  
Field Model ◽  
Second Law Of Thermodynamics ◽  
Matter Content ◽  
Second Law ◽  
Correct Description ◽  
Thermodynamic Consideration ◽  
Scalar Field Model ◽  
The Past ◽  
Generalized Second Law

Abstract Thawing and freezing quintessence models are compared thermodynamically. Both of them are found to disobey the generalized second law of thermodynamics. However, for freezing models, there is still a scope as this breakdown occurs in the past, deep inside the radiation dominated era, when a standard scalar field model with a pressureless matter is not a correct description of the matter content. The thawing model has a pathological breakdown in terms of thermodynamics in a finite future.

Dynamic study of Weyl tensor corrected f(R) gravity

2021 ◽  
Author(s):  
Abdul Malik Sultan ◽  
Abdul Jawad
Keyword(s):  
Weyl Tensor ◽  
Thermal Equilibrium ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Second Law Of Thermodynamics ◽  
Positive Behavior ◽  
Second Law ◽  
Generalized Second Law ◽  
Equation Of State Parameter ◽  
Thermal Equilibrium Condition

We investigate the cosmological and thermodynamic aspects of Weyl tensor corrected [Formula: see text] gravity. For this purpose, we assume some well-known cosmological bouncing scenarios such as symmetric bounce cosmology, oscillatory cosmology, matter bounce cosmology, little rip cosmology, superbounce cosmology and develop some cosmological parameters. For instance, the equation of state parameter [Formula: see text] describes the quintessence phase for symmetric bounce cosmology, vacuum phase for oscillatory, little rip and matter bounce cosmology while it gives both quintessence and vacuum phases for matter bounce cosmology. It is also observed that the squared speed of sound [Formula: see text] gives positive behavior for all models resulting in that the models assumed are stable. We evaluate generalized second law of thermodynamics which remains valid for all cosmological models except symmetric bounce cosmology. Moreover, we also investigate the thermal equilibrium condition [Formula: see text] and found its validity for all models except symmetric bounce cosmological model.

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