Gauge-invariant cosmological perturbations
Abstract
The physical interpretation of perturbations of homogeneous, isotropic cosmological models in the early Universe, when the perturbation is larger than the particle horizon, is clarified by defining a complete set of gauge-invariant variables. The linearized perturbation equations written in these variables are simpler than the usual versions, and easily accommodate an arbitrary background equation of state, entropy perturbations, and anisotropic pressure perturbations. Particular attention is paid to how a scalar (density) perturbation might be generated by stress perturbations at very early times, when the non-gauge-invariant perturbation in the density itself is ill-defined. The amplitude of the fractional energy density perturbation at the particle horizon cannot be larger, in order of magnitude, than the maximum ratio of the stress perturbation to the background energy density at any earlier time, unless the perturbation is inherent in the initial singularity.
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Inflation predicts the observed spectrum of primordial density fluctuations.
“In addition, inflation predicts the observed spectrum of primordial density fluctuations (Bardeen 1980;Mukhanov et al. 1992).”
From UNIVERSE IN A BLACK HOLE IN EINSTEIN–CARTAN GRAVITY (2016) · cites this paper as Bardeen 1980
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UNIVERSE IN A BLACK HOLE IN EINSTEIN–CARTAN GRAVITY
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- Authors
- Bardeen, J. M.
- Affiliations
- Institute for Advanced Study (US)
- Corresponding author
- Bardeen, James M.
- Venue
- Physical Review D
- Publisher
- American Physical Society (APS)
- Published
- 1980-10-15
- Volume
- 22
- Issue
- 8
- Pages
- 1882-1905
- ISSN
- 0556-2821 (ISSN-L)
- OpenAlex
- W2169912865
- Cited by
- 2,393
- References
- 1
- Citations by year
- 2026: 58 · 2025: 99 · 2024: 62 · 2023: 67 · 2022: 63 · 2021: 87 · 2020: 100 · 2019: 78 · 2018: 84 · 2017: 74 · 2016: 104 · 2015: 97 · 2014: 94 · 2013: 85 · 2012: 89
- FWCI
- 7.37
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields (publishedVersion)
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Cosmology and Gravitation Theories
- Physical Sciences › Physics and Astronomy › Statistical and Nonlinear Physics › Noncommutative and Quantum Gravity Theories
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
- Keywords
- gauge-invariant variables, cosmological perturbations, early universe, particle horizon, entropy perturbations, stress perturbation, initial singularity, linearized perturbation equations, equation of state
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