Backreaction in Cosmology
arXiv:2106.06043 · doi:10.3389/fspas.2021.692198
Abstract
In this review, we investigate the question of backreaction in different approaches to cosmological perturbation theory, and with a special focus on quantum theoretical aspects. By backreaction, we refer here to the effects of matter field or cosmological inhomogeneities on the homogeneous dynamical background degrees of freedom of cosmology. We begin with an overview of classical cosmological backreaction which is ideally suited for physical situations in the late time Universe. We then proceed backwards in time, considering semiclassical approaches such as semiclassical or stochastic (semiclassical) gravity which take quantum effects of the perturbations into account. Finally, we review approaches to backreaction in quantum cosmology that should apply to the very early Universe where classical and semiclassical approximations break down. The main focus is on a recently proposed implementation of backreaction in quantum cosmology using a Born-Oppenheimer inspired method.
41 pages
References in corpus (30)
- Large Magellanic Cloud Cepheid Standards Provide a 1% Foundation for the Determination of the Hubble Constant and Stronger Evidence for Physics Beyond LambdaCDM
- The Megamaser Cosmology Project. XIII. Combined Hubble constant constraints
- The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Large-scale Structure Catalogs for Cosmological Analysis
- Generation of fluctuations during inflation: comparison of stochastic and field-theoretic approaches
- A new framework for analyzing the effects of small scale inhomogeneities in cosmology
- Towards Spinfoam Cosmology
- How well is our universe described by an FLRW model?
- Light-cone averages in a swiss-cheese universe
- Scale dependence of cosmological backreaction
- Szekeres Swiss-Cheese model and supernova observations
- Stepping out of Homogeneity in Loop Quantum Cosmology
- The influence of structure formation on the cosmic expansion
- Stable cosmological models driven by a free quantum scalar field
- Cosmological Backreaction from Perturbations
- The Spatial Averaging Limit of Covariant Macroscopic Gravity - Scalar Corrections to the Cosmological Equations
- Cosmological Perturbation Theory in Slow-Roll Spacetimes
- Unique Fock quantization of scalar cosmological perturbations
- Another look at redshift drift and the backreaction conjecture
- Unitarity of quantum-gravitational corrections to primordial fluctuations in the Born-Oppenheimer approach
- Redshift propagation equations in the Szekeres models
- Searching for signals of inhomogeneity using multiple probes of the cosmic expansion rate H(z)
- The Averaging Problem in Cosmology and Macroscopic Gravity
- Cosmic Inhomogeneities and the Average Cosmological Dynamics
- Backreaction during inflation: a physical gauge invariant formulation
- Hybrid Models in Loop Quantum Cosmology
- Averaging Robertson-Walker Cosmologies
- Multipole decomposition of redshift drift -- model independent mapping of the expansion history of the Universe
- Generalized covariant prescriptions for averaging cosmological observables
- Dynamical Backreaction in Robertson-Walker Spacetime
- Quantum Spacetime Instability and Breakdown of Semiclassical Gravity