scholarly journals CYCLIC UNIVERSE WITH QUINTOM MATTER IN LOOP QUANTUM COSMOLOGY

2009 ◽  
Vol 24 (15) ◽  
pp. 1237-1246 ◽  
Author(s):  
HUA-HUI XIONG ◽  
TAOTAO QIU ◽  
YI-FU CAI ◽  
XINMIN ZHANG
Keyword(s):  
Scalar Field ◽  
Quantum Cosmology ◽  
Model Building ◽  
Numerical Calculations ◽  
Loop Quantum Cosmology ◽  
Cyclic Universe

In this paper, we study the possibility of model building of cyclic universe with Quintom matter in the framework of Loop Quantum Cosmology. After a general demonstration, we provide two examples, one with double-fluid and another double-scalar field, to show how such a scenario is obtained. Analytical and numerical calculations are both presented in the paper.

scholarly journals Noncommutative Friedmann equations in effective LQC

2020 ◽  
Vol 29 (06) ◽  
pp. 2050039
Author(s):  
Luis Rey Díaz-Barrón ◽  
Abraham Espinoza-García ◽  
S. Pérez-Payán ◽  
J. Socorro
Keyword(s):  
Scalar Field ◽  
Effective Potential ◽  
Quantum Cosmology ◽  
Equations Of Motion ◽  
Loop Quantum Cosmology ◽  
Friedmann Equations ◽  
Noncommutative Version ◽  
Previous Proposal ◽  
Free Scalar ◽  
Raychaudhuri Equations

In this work, we construct a noncommutative version of the Friedmann equations in the framework of effective loop quantum cosmology, extending and applying the ideas presented in a previous proposal by some of the authors. The model under consideration is a flat FRW spacetime with a free scalar field. First, noncommutativity in the momentum sector is introduced. We establish the noncommutative equations of motion and obtain the corresponding exact solutions. Such solutions indicate that the bounce is preserved, in particular, the energy density is the same as in the standard LQC. We also construct an extension of the modified Friedmann equations arising in effective LQC which incorporates corrections due to noncommutativity, and argue that an effective potential is induced. This, in turn, leads us to investigate the possibility of an inflationary era. Finally, we obtain the Friedmann and the Raychaudhuri equations when implementing noncommutativity in the configuration sector. In this case, no effective potential is induced.

scholarly journals The Effect of a Positive Cosmological Constant on the Bounce of Loop Quantum Cosmology

Mathematics ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 186
Author(s):  
Mercedes Martín-Benito ◽  
Rita B. Neves
Keyword(s):  
Scalar Field ◽  
Cosmological Constant ◽  
Quantum Cosmology ◽  
Quantum Dynamics ◽  
Solvable Model ◽  
Massless Scalar ◽  
Loop Quantum Cosmology ◽  
Massless Scalar Field ◽  
Positive Cosmological Constant ◽  
Semiclassical States

We provide an analytical solution to the quantum dynamics of a flat Friedmann-Lemaître- Robertson-Walker model with a massless scalar field in the presence of a small and positive cosmological constant, in the context of Loop Quantum Cosmology. We use a perturbative treatment with respect to the model without a cosmological constant, which is exactly solvable. Our solution is approximate, but it is precisely valid at the high curvature regime where quantum gravity corrections are important. We compute explicitly the evolution of the expectation value of the volume. For semiclassical states characterized by a Gaussian spectral profile, the introduction of a positive cosmological constant displaces the bounce of the solvable model to lower volumes and to higher values of the scalar field. These displacements are state dependent, and in particular, they depend on the peak of the Gaussian profile, which measures the momentum of the scalar field. Moreover, for those semiclassical states, the bounce remains symmetric, as in the vanishing cosmological constant case. However, we show that the behavior of the volume is more intricate for generic states, leading in general to a non-symmetric bounce.

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).

scholarly journals Inflation from non-minimally coupled scalar field in loop quantum cosmology

2013 ◽  
Vol 2013 (06) ◽  
pp. 010-010 ◽  
Author(s):  
Michał Artymowski ◽  
Andrea Dapor ◽  
Tomasz Pawłowski
Keyword(s):  
Scalar Field ◽  
Quantum Cosmology ◽  
Loop Quantum Cosmology

scholarly journals Noncommutativity in Effective Loop Quantum Cosmology

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Abraham Espinoza-García ◽  
Efraín Torres-Lomas ◽  
Sinuhé Pérez-Payán ◽  
Luis Rey Díaz-Barrón
Keyword(s):  
Scalar Field ◽  
Quantum Cosmology ◽  
Free Field ◽  
Matter Field ◽  
Field Energy ◽  
Loop Quantum Cosmology ◽  
Free Scalar ◽  
Key Features ◽  
Field Energy Density ◽  
The One

We construct a noncommutative extension of the Loop Quantum Cosmology effective scheme for the flat FLRW model with a free scalar field via a theta deformation. Firstly, a deformation is implemented in the configuration sector, among the holonomy variable and the matter degree of freedom. We show that this type of noncommutativity retains, to some degree, key features of the Loop Quantum Cosmology paradigm for a free field. Secondly, a deformation is implemented in the momentum sector, among the momentum associated with the holonomy variable and the momentum associated with the matter field. We show that in this latter case the scalar field energy density is the same as the one in standard Loop Quantum Cosmology.

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.

Stability analysis of Einstein’s universe in loop quantum cosmology

2020 ◽  
Vol 35 (28) ◽  
pp. 2050166
Author(s):  
Eamon Mc Caughey
Keyword(s):  
General Relativity ◽  
Stability Analysis ◽  
Quantum Cosmology ◽  
Loop Quantum Gravity ◽  
Hamiltonian Structure ◽  
Loop Quantum Cosmology ◽  
Universe Model ◽  
Integrals Of Motion ◽  
Cyclic Universe ◽  
The Stability

A stability analysis of Einstein’s universe in both classical general relativity and semiclassical loop quantum cosmology regimes is presented. The stability properties of the general relativity model are significantly altered due to loop quantum gravity corrections. Comparisons between both dynamical systems are considered on the basis of these modifications. The loop quantum cosmology solutions are restricted to an open universe model [Formula: see text] and represent a cyclic universe. The integrals of motion for both systems are found and their Hamiltonian structure determined.

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