Hybrid Models in Loop Quantum Cosmology

Abstract

In the framework of Loop Quantum Cosmology, 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 Loop Quantum Cosmology

Invited review article for the special issue of the International Journal of Modern Physics D on Loop Quantum Cosmology

References in corpus (17)

• Quantum Nature of the Big Bang: Improved dynamics
• Hybrid Quantum Gowdy Cosmology: Combining Loop and Fock Quantizations
• Hybrid quantization of an inflationary universe
• Inhomogeneous Loop Quantum Cosmology: Hybrid Quantization of the Gowdy Model
• Cosmological perturbations in Hybrid Loop Quantum Cosmology: Mukhanov-Sasaki variables
• Hybrid Quantum Cosmology: Combining Loop and Fock Quantizations
• Quantum Gowdy $T^3$ model: A uniqueness result
• Uniqueness of the Fock quantization of the Gowdy $T^3$ model
• Quantum Gowdy $T^3$ model: A unitary description
• Uniqueness of the Fock quantization of scalar fields in spatially flat cosmological spacetimes
• Unique Fock quantization of scalar cosmological perturbations
• Matter in inhomogeneous loop quantum cosmology: the Gowdy $T^3$ model
• Uniqueness of the Fock quantization of fields with unitary dynamics in nonstationary spacetimes
• Uniqueness of the Fock quantization of scalar fields and processes with signature change in cosmology
• Hamiltonian Dynamics of Linearly Polarized Gowdy Models Coupled to Massless Scalar Fields
• Modeling effective FRW cosmologies with perfect fluids from states of the hybrid quantum Gowdy model
• Casimir effect in a quantum space-time