scholarly journals Nonadiabatic evolution of primordial perturbations and non-Gaussinity in hybrid approach of loop quantum cosmology

2018 ◽  
Vol 98 (10) ◽  
Author(s):  
Qiang Wu ◽  
Tao Zhu ◽  
Anzhong Wang
Keyword(s):  
Quantum Cosmology ◽  
Hybrid Approach ◽  
Loop Quantum Cosmology

scholarly journals Hybrid Loop Quantum Cosmology: An Overview

2021 ◽  
Vol 8 ◽  
Author(s):  
Beatriz Elizaga Navascués ◽  
Guillermo A. Mena Marugán
Keyword(s):  
Quantum Cosmology ◽  
Degrees Of Freedom ◽  
Hybrid Approach ◽  
Loop Quantum Cosmology ◽  
Main Challenge ◽  
Cosmological Observations ◽  
Linearly Polarized ◽  
Homogeneous Background ◽  
Gowdy Spacetimes ◽  
Physical Consequences

Loop Quantum Gravity is a nonperturbative and background independent program for the quantization of General Relativity. Its underlying formalism has been applied successfully to the study of cosmological spacetimes, both to test the principles and techniques of the theory and to discuss its physical consequences. These applications have opened a new area of research known as Loop Quantum Cosmology. The hybrid approach addresses the quantization of cosmological systems that include fields. This proposal combines the description of a finite number of degrees of freedom using Loop Quantum Cosmology, typically corresponding to a homogeneous background, and a Fock quantization of the field content of the model. In this review we first present a summary of the foundations of homogeneous Loop Quantum Cosmology and we then revisit the hybrid quantization approach, applying it to the study of Gowdy spacetimes with linearly polarized gravitational waves on toroidal spatial sections, and to the analysis of cosmological perturbations in preinflationary and inflationary stages of the Universe. The main challenge is to extract predictions about quantum geometry effects that eventually might be confronted with cosmological observations. This is the first extensive review of the hybrid approach in the literature on Loop Quantum Cosmology.

scholarly journals Chimera: a hybrid approach to numerical loop quantum cosmology

2013 ◽  
Vol 31 (2) ◽  
pp. 025013 ◽  
Author(s):  
Peter Diener ◽  
Brajesh Gupt ◽  
Parampreet Singh
Keyword(s):  
Quantum Cosmology ◽  
Hybrid Approach ◽  
Loop Quantum Cosmology

scholarly journals Hybrid models in loop quantum cosmology

2016 ◽  
Vol 25 (08) ◽  
pp. 1642007 ◽  
Author(s):  
Beatriz Elizaga Navascués ◽  
Mercedes Martín-Benito ◽  
Guillermo A. Mena Marugán
Keyword(s):  
Quantum Cosmology ◽  
Degrees Of Freedom ◽  
Hybrid Approach ◽  
Loop Quantum Cosmology ◽  
Hamiltonian Constraint ◽  
Hybrid Strategy ◽  
Fock Representation ◽  
Zero Modes ◽  
Inhomogeneous Models ◽  
Global Zero

In the framework of Loop Quantum Cosmology (LQC), inhomogeneous models are usually quantized by means of a hybrid approach that combines loop quantization techniques with standard quantum field theory methods. This approach is based on a splitting of the phase space in a homogeneous sector, formed by global, zero-modes and an inhomogeneous sector, formed by the remaining, infinite number of modes, that describe the local degrees of freedom. Then, the hybrid quantization is attained by adopting a loop representation for the homogeneous gravitational sector, while a Fock representation is used for the inhomogeneities. The zero-mode of the Hamiltonian constraint operator couples the homogeneous and inhomogeneous sectors. The hybrid approach, therefore, is expected to provide a suitable quantum theory in regimes where the main quantum effects of the geometry are those affecting the zero-modes, while the inhomogeneities, still being quantum, can be treated in a more conventional way. This hybrid strategy was first proposed for the simplest cosmological midisuperspaces: the Gowdy models, and it has been later applied to the case of cosmological perturbations. This paper reviews the construction and main applications of hybrid LQC.

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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