scholarly journals Discretization parameter and operator ordering in loop quantum cosmology with the cosmological constant

2011 ◽  
Vol 83 (10) ◽  
Author(s):  
Tomo Tanaka ◽  
Fumitoshi Amemiya ◽  
Masahiro Shimano ◽  
Tomohiro Harada ◽  
Takashi Tamaki
Keyword(s):  
Cosmological Constant ◽  
Quantum Cosmology ◽  
Loop Quantum Cosmology ◽  
Discretization Parameter ◽  
Operator Ordering

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 CAUSAL LOOP QUANTUM COSMOLOGY IN MOMENTUM SPACE

2009 ◽  
Vol 18 (01) ◽  
pp. 83-93
Author(s):  
ALI SHOJAI ◽  
FATIMAH SHOJAI
Keyword(s):  
Cosmological Constant ◽  
Momentum Space ◽  
Quantum Cosmology ◽  
Cosmological Solution ◽  
Dynamical Variable ◽  
Loop Quantum Cosmology ◽  
Causal Interpretation ◽  
Causal Loop ◽  
Bohmian Trajectories

We shall show that it is possible to make a causal interpretation of loop quantum cosmology using the momentum as the dynamical variable. We shall show that one can derive Bohmian trajectories. For a sample cosmological solution with cosmological constant, the trajectory is plotted.

scholarly journals On the Geometry of No-Boundary Instantons in Loop Quantum Cosmology

Universe ◽  
2019 ◽  
Vol 5 (1) ◽  
pp. 22 ◽  
Author(s):  
Suddhasattwa Brahma ◽  
Dong-han Yeom
Keyword(s):  
Cosmological Constant ◽  
Path Integral ◽  
Quantum Cosmology ◽  
Einstein Gravity ◽  
Peculiar Feature ◽  
Loop Quantum Cosmology ◽  
Quantum Geometry

We study the geometry of Euclidean instantons in loop quantum cosmology (LQC) such as those relevant for the no-boundary proposal. Confining ourselves to the simplest case of a cosmological constant in minisuperspace cosmologies, we analyze solutions of the semiclassical (Euclidean) path integral in LQC. We find that the geometry of LQC instantons have the peculiar feature of an infinite tail which distinguishes them from Einstein gravity. Moreover, due to quantum-geometry corrections, the small-a behaviour of these instantons seem to naturally favor a closing-off of the geometry in a regular fashion, as was originally proposed for the no-boundary wavefunction.

scholarly journals Universe’s memory and spontaneous coherence in loop quantum cosmology

2016 ◽  
Vol 25 (08) ◽  
pp. 1642013 ◽  
Author(s):  
Tomasz Pawłowski
Keyword(s):  
Cosmological Constant ◽  
Present State ◽  
Quantum Cosmology ◽  
A Priori ◽  
Loop Quantum Cosmology ◽  
Positive Cosmological Constant ◽  
Isotropic Universe ◽  
Constant Of Motion ◽  
Universe Evolution

The quantum bounce a priori connects several (semi)classical epochs of universe evolution, however determining if and how well the semiclassicality is preserved in this transition is highly nontrivial. We review the present state of knowledge in that regards in the isotropic sector of loop quantum cosmology (LQC). This knowledge is next extended by studies of an isotropic universe admitting positive cosmological constant (featuring an infinite chain of large universe epochs). It is also shown, that such universe always admits a semiclassical epoch thanks to spontaneous coherence, provided it is semiclassical in certain constant of motion playing the role of energy.

scholarly journals Bootstrapped Newtonian Cosmology and the Cosmological Constant Problem

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 358
Author(s):  
Roberto Casadio ◽  
Andrea Giusti
Keyword(s):  
Black Holes ◽  
Cosmological Constant ◽  
Quantum Cosmology ◽  
Quantum Physics ◽  
Gravitational Interaction ◽  
Newtonian Gravity ◽  
Cosmological Constant Problem ◽  
Newtonian Cosmology ◽  
Natural Solution ◽  
The Impact

Bootstrapped Newtonian gravity was developed with the purpose of estimating the impact of quantum physics in the nonlinear regime of the gravitational interaction, akin to corpuscular models of black holes and inflation. In this work, we set the ground for extending the bootstrapped Newtonian picture to cosmological spaces. We further discuss how such models of quantum cosmology can lead to a natural solution to the cosmological constant problem.

scholarly journals Covariant entropy bound and loop quantum cosmology

2008 ◽  
Vol 78 (6) ◽  
Author(s):  
Abhay Ashtekar ◽  
Edward Wilson-Ewing
Keyword(s):  
Quantum Cosmology ◽  
Loop Quantum Cosmology ◽  
Entropy Bound
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