Separate universes in loop quantum cosmology: framework and applications

Abstract

I present a streamlined review of how the separate universe approach to cosmological perturbation theory can be used to study the dynamics of long-wavelength scalar perturbations in loop quantum cosmology, and then use it to calculate how long-wavelength curvature perturbations evolve across the loop quantum cosmology bounce assuming a constant equation of state. A similar calculation is possible for tensor modes using results from a complementary approach to cosmological perturbation theory in loop quantum cosmology based on an effective Hamiltonian constraint. An interesting result is that the tensor-to-scalar ratio can be suppressed or amplified by quantum gravity effects during the bounce, depending on the equation of state of the matter field dominating the dynamics. In particular, if the equation of state lies between -1/3 and 1, the value of the tensor-to-scalar ratio will be suppressed during the bounce, in some cases significantly.

13 pages, v2: Title changed, clarifications and references added. Prepared for submission to IJMPD special issue on Loop Quantum Cosmology

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Cited by in corpus (19)

• Emergent Friedmann dynamics with a quantum bounce from quantum gravity condensates
• Pre-inflationary universe in loop quantum cosmology
• The universe as a quantum gravity condensate
• Bouncing cosmologies with dark matter and dark energy
• Testing loop quantum cosmology
• Matter bounce cosmology with a generalized single field: non-Gaussianity and an extended no-go theorem
• Loop Quantum Cosmology: A brief review
• The separate universe framework in group field theory condensate cosmology
• Effective dynamics of scalar cosmological perturbations from quantum gravity
• Preinflationary perturbations from the closed algebra approach in loop quantum cosmology
• Loop quantum cosmology: relation between theory and observations
• A first step towards the inflationary trans-planckian problem treatment in Loop Quantum Cosmology
• Gravitational Particle Production and the Validity of Effective Descriptions in Loop Quantum Cosmology
• Running of the Spectral index in Deformed Matter Bounce Scenarios with Hubble-rate-dependent Dark Energy
• Gauge-invariant perturbations at a quantum gravity bounce
• A quasi-matter bounce equivalent to Starobinsky inflation
• Alternative effective mass functions in the modified Mukhanov-Sasaki equation of loop quantum cosmology
• Regularization of the cosmological sector of loop quantum gravity with bosonic matter and the related problems with general covariance of quantum corrections
• Non singular M theory Universe in Loop Quantum Cosmology -- inspired Models