scholarly journals Preinflationary perturbations from the closed algebra approach in loop quantum cosmology

2019 ◽  
Vol 99 (10) ◽  
Author(s):  
Bao-Fei Li ◽  
Tao Zhu ◽  
Anzhong Wang ◽  
Klaus Kirsten ◽  
Gerald Cleaver ◽  
...  
Keyword(s):  
Quantum Cosmology ◽  
Loop Quantum Cosmology ◽  
Closed Algebra ◽  
Algebra Approach

scholarly journals The perturbed universe in the deformed algebra approach of loop quantum cosmology

2016 ◽  
Vol 25 (08) ◽  
pp. 1642003 ◽  
Author(s):  
Julien Grain
Keyword(s):  
Quantum Gravity ◽  
Quantum Cosmology ◽  
Initial Conditions ◽  
Power Spectra ◽  
Quantum Corrections ◽  
Loop Quantum Cosmology ◽  
Algebra Approach ◽  
Deformed Algebra ◽  
Contracting Phase ◽  
The Universe

Loop Quantum Cosmology (LQC) is a tentative approach to model the universe down to the Planck era where quantum gravity settings are needed. The quantization of the universe as a dynamical spacetime is inspired by Loop Quantum Gravity (LQG) ideas. In addition, LQC could bridge contact with astronomical observations, and thus potentially investigate quantum cosmology modelings in the light of observations. To do so however, modeling both the background evolution and its perturbations is needed. The latter described cosmic inhomogeneities that are the main cosmological observables. In this context, we present the so-called deformed algebra approach implementing the quantum corrections to the perturbed universe at an effective level by taking great care of gauge issues. We particularly highlight that in this framework, the algebra of hypersurface deformation receives quantum corrections, and we discuss their meaning. The primordial power spectra of scalar and tensor inhomogeneities are then presented, assuming initial conditions are set in the contracting phase preceding the quantum bounce and the well-known expanding phase of the cosmic history. These spectra are subsequently propagated to angular power spectra of the anisotropies of the cosmic microwave background. It is then shown that regardless of the choice for the initial conditions inside the effective approach for the background evolution (except that they are set in the contracting phase), the predicted angular power spectra of the polarized [Formula: see text]-modes exceed the upper bound currently set by observations. The exclusion of this specific version of LQC establishes the falsifiability of the approach, though one shall not conclude here that either LQC or LQG excluded.

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

scholarly journals Measuring the effects of loop quantum cosmology in the CMB data

2017 ◽  
Vol 26 (12) ◽  
pp. 1743023 ◽  
Author(s):  
Spyros Basilakos ◽  
Vahid Kamali ◽  
Ahmad Mehrabi
Keyword(s):  
Power Spectrum ◽  
Spectral Index ◽  
Excellent Agreement ◽  
Quantum Cosmology ◽  
Loop Quantum Cosmology ◽  
Alternative Scenario ◽  
Slow Roll ◽  
Scalar Spectral Index ◽  
Robust Prediction ◽  
Scalar Fluctuation

In this paper we investigate the observational signatures of Loop Quantum Cosmology (LQC) in the CMB data. First, we concentrate on the dynamics of LQC and we provide the basic cosmological functions. We then obtain the power spectrum of scalar and tensor perturbations in order to study the performance of LQC against the latest CMB data. We find that LQC provides a robust prediction for the main slow-roll parameters, like the scalar spectral index and the tensor-to-scalar fluctuation ratio, which are in excellent agreement within [Formula: see text] with the values recently measured by the Planck collaboration. This result indicates that LQC can be seen as an alternative scenario with respect to that of standard inflation.

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