scholarly journals Thermodynamics in Loop Quantum Cosmology

2009 ◽  
Vol 2009 ◽  
pp. 1-9 ◽  
Author(s):  
Li-Fang Li ◽  
Jian-Yang Zhu
Keyword(s):  
Quantum Cosmology ◽  
Apparent Horizon ◽  
Friedmann Equation ◽  
Gravitational Energy ◽  
Effective Density ◽  
Loop Quantum Cosmology ◽  
Thermodynamic Quantities ◽  
Effective Pressure ◽  
The Universe ◽  
Friedmann Robertson Walker

Loop quantum cosmology (LQC) is very powerful to deal with the behavior of early universe. Moreover, the effective loop quantum cosmology gives a successful description of the universe in the semiclassical region. We consider the apparent horizon of the Friedmann-Robertson-Walker universe as a thermodynamical system and investigate the thermodynamics of LQC in the semiclassical region. The effective density and effective pressure in the modified Friedmann equation from LQC not only determine the evolution of the universe in LQC scenario but also are actually found to be the thermodynamic quantities. This result comes from the energy definition in cosmology (the Misner-Sharp gravitational energy) and is consistent with thermodynamic laws. We prove that within the framework of loop quantum cosmology, the elementary equation of equilibrium thermodynamics is still valid.

scholarly journals Thermodynamics in new model of loop quantum cosmology

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Xiangdong Zhang
Keyword(s):  
Quantum Cosmology ◽  
Apparent Horizon ◽  
Friedmann Equation ◽  
High Energy ◽  
Effective Density ◽  
Loop Quantum Cosmology ◽  
Thermodynamic Quantities ◽  
Effective Pressure ◽  
New Model ◽  
The Universe

AbstractThe thermodynamic properties of loop quantum cosmology (LQC) without considering the Lorentz term were established in Li and Zhu (Adv High Energy Phys 2009:905705, 2009). In this paper, we extend this result to the recent proposed new model of LQC with the Lorentz term. We investigate the thermodynamics of LQC on the apparent horizon of the Friedmann–Lematre–Robertson–Walker universe. The result shows that the effective density and effective pressure in the modified Friedmann equation of LQC not only determines the evolution of the universe but can also serve as the thermodynamic quantities. Moreover, with the help of the Misner–Sharp energy, the first law of thermodynamics of the LQC is still valid as expected. This in turn endows precise physical meaning to the effective matter density $$\rho _{eff}$$ ρ eff and the effective pressure $$P_{eff}$$ P eff .

scholarly journals EQUIPARTITION OF ENERGY AND THE FIRST LAW OF THERMODYNAMICS AT THE APPARENT HORIZON

2011 ◽  
Vol 20 (04) ◽  
pp. 553-559 ◽  
Author(s):  
FU-WEN SHU ◽  
YUNGUI GONG
Keyword(s):  
Apparent Horizon ◽  
Friedmann Equation ◽  
Consistency Check ◽  
First Law Of Thermodynamics ◽  
A Value ◽  
Cosmological Observations ◽  
Equipartition Law ◽  
Equipartition Of Energy ◽  
The Universe ◽  
Friedmann Robertson Walker

We apply the holographic principle and the equipartition law of energy to the apparent horizon of a Friedmann–Robertson–Walker universe and derive the Friedmann equation describing the dynamics of the universe. We also show that the equipartition law of energy can be interpreted as the first law of thermodynamics at the apparent horizon. The consistency check shows that our derivation is correct for –1 < w < –(1/3), a value that matches the recent cosmological observations.

scholarly journals Creation of particles in a cyclic universe driven by loop quantum cosmology

2015 ◽  
Vol 24 (08) ◽  
pp. 1550062 ◽  
Author(s):  
Yaser Tavakoli ◽  
Júlio C. Fabris
Keyword(s):  
Scalar Field ◽  
Quantum Cosmology ◽  
Particle Production ◽  
Friedmann Equation ◽  
Big Bang ◽  
Loop Quantum Cosmology ◽  
Late Time ◽  
Background Density ◽  
The Future ◽  
The Universe

We consider an isotropic and homogeneous universe in loop quantum cosmology (LQC). We assume that the matter content of the universe is dominated by dust matter in early time and a phantom matter at late time which constitutes the dark energy component. The quantum gravity modifications to the Friedmann equation in this model indicate that the classical big bang singularity and the future big rip singularity are resolved and are replaced by quantum bounce. It turns out that the big bounce and recollapse in the herein model contribute to a cyclic scenario for the universe. We then study the quantum theory of a massive, nonminimally coupled scalar field undergoing cosmological evolution from primordial bounce towards the late time bounce. In particular, we solve the Klein–Gordon equation for the scalar field in the primordial and late time regions, in order to investigate particle production phenomena at late time. By computing the energy density of created particles at late time, we show that this density is negligible in comparison to the quantum background density at Planck era. This indicates that the effects of quantum particle production do not influence the future bounce.

Cosmology of the generalized model of LQG

2020 ◽  
Vol 35 (30) ◽  
pp. 2050247
Author(s):  
Surajit Chattopadhyay ◽  
Martiros Khurshudyan ◽  
K. Myrzakulov ◽  
Antonio Pasqua ◽  
Ratbay Myrzakulov
Keyword(s):  
Scalar Field ◽  
Quantum Cosmology ◽  
Friedmann Equation ◽  
Loop Quantum Cosmology ◽  
De Sitter ◽  
Complicated Case ◽  
Friedmann Equations ◽  
Cosmological Solutions ◽  
Text Model ◽  
Friedmann Robertson Walker

In this paper, we study the main cosmological properties of the classical Friedmann equations in the case of homogeneous and isotropic Friedmann–Robertson–Walker Universe and we also generalized the expression of the Friedmann equation in the case of Loop Quantum Cosmology (LQC). Considering the [Formula: see text]-model, we found the solutions of the equations considered for two particular cases, i.e. [Formula: see text] (i.e. the de Sitter solution) and [Formula: see text]. Moreover, we considered and studied two exact cosmological solutions of the [Formula: see text]-model, in particular the power-law and the exponential ones. Moreover, we also considered a third more complicated case and we derived the solution for an arbitrary function of the time [Formula: see text]. A scalar field description of the model is presented by constructing its self-interacting potential.

The evolutionary pictures for phantom field in loop quantum cosmology

2019 ◽  
Vol 28 (15) ◽  
pp. 1950170
Author(s):  
Kui Xiao
Keyword(s):  
Dark Matter ◽  
Quantum Cosmology ◽  
Scalar Fields ◽  
Chaplygin Gas ◽  
Loop Quantum Cosmology ◽  
Phantom Field ◽  
Dynamical Behaviors ◽  
Slow Roll ◽  
The Universe ◽  
Slow Roll Inflation

The evolutionary pictures for phantom field in loop quantum cosmology are discussed in this paper. Comparing the dynamical behaviors of the phantom field with one of the canonical scalar fields in loop quantum cosmology scenario, we found that the [Formula: see text] phase trajectories are the same, but the [Formula: see text] phase-spaces are very different, and the phantom field with considering potentials can drive neither super inflation nor slow-roll inflation in loop quantum cosmology (LQC) scenario. While the universe is filled with multiple dark fluids, to ensure that the condition [Formula: see text] does not violate, the energy density of dark matter [Formula: see text] and the equation-of-state of phantom field [Formula: see text] should satisfy the condition [Formula: see text] at the bounce point. If this constraint condition holds, the universe can enter an inflationary stage, and it is possible to unify the description of phantom field, dark matter and inflation. We introduced a toy model which has the same form of the general Chaplygin gas to unify the dark energy, dark matter and slow-roll inflation, and the slow-roll inflation of the toy model has also been discussed.

1-loop quantum cosmology: the contributions of matter fields to the wavefunction of the universe

1992 ◽  
Vol 9 (2) ◽  
pp. L27-L32 ◽  
Author(s):  
A O Barvinsky ◽  
A Y Kamenshchik ◽  
I P Karmazin ◽  
I V Mishakov
Keyword(s):  
Quantum Cosmology ◽  
Loop Quantum Cosmology ◽  
The Universe ◽  
Matter Fields

A unified picture of cosmological entropy on apparent horizon in F(R, G) gravity

2017 ◽  
Vol 32 (33) ◽  
pp. 1750182 ◽  
Author(s):  
Ali İhsan Keskin ◽  
Irfan Acikgoz
Keyword(s):  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Hawking Temperature ◽  
Second Law ◽  
Field Equations ◽  
Frw Universe ◽  
Generalized Second Law ◽  
History Of ◽  
The Universe ◽  
Friedmann Robertson Walker

In this study, the validity of the generalized second law of thermodynamics (GSLT) has been investigated in F(R, G) gravity. We consider that the boundary of the universe is surrounded by an apparent horizon in the spatially flat Friedmann–Robertson–Walker (FRW) universe, and we take into account the Hawking temperature on the horizons. The unified solutions of the field equations corresponding to gravity theory have been applied to the validity of the GSLT frame, and in this way, both the solutions have been verified and all the expansion history of the universe has been shown in a unified picture.

scholarly journals EMERGENT UNIVERSE WITH EXOTIC MATTER IN LOOP QUANTUM COSMOLOGY, DGP BRANE-WORLD AND KALUZA–KLEIN COSMOLOGY

2012 ◽  
Vol 27 (33) ◽  
pp. 1250189 ◽  
Author(s):  
PRABIR RUDRA
Keyword(s):  
Scalar Field ◽  
Quantum Cosmology ◽  
Brane World ◽  
Loop Quantum Cosmology ◽  
Tachyonic Field ◽  
Normal Matter ◽  
Emergent Scenario ◽  
Phantom Scalar ◽  
The Universe ◽  
Kaluza Klein

In this work we have investigated the emergent scenario of the Universe described by loop quantum cosmology model, DGP brane model and Kaluza–Klein cosmology. Scalar field along with barotropic fluid as normal matter is considered as the matter content of the Universe. In loop quantum cosmology it is found that the emergent scenario is realized with the imposition of some conditions on the value of the density of normal matter in case of normal and phantom scalar field. This is a surprising result indeed considering the fact that scalar field is the dominating matter component! In case of tachyonic field, emergent scenario is realized with some constraints on the value of ρ1 for both normal and phantom tachyon. In case of DGP brane-world realization of an emergent scenario is possible almost unconditionally for normal and phantom fields. Plots and table have been generated to testify this fact. In case of tachyonic field emergent scenario is realized with some constraints on [Formula: see text]. In Kaluza–Klein cosmology emergent scenario is possible only for a closed Universe in case of normal and phantom scalar field. For a tachyonic field, realization of emergent Universe is possible for all models (closed, open and flat).

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