Conserved cosmological perturbations

By D. Lyth, D. Wands. 2003

149 citations recorded by the source corpus.

A conserved cosmological perturbation is associated with each quantity whose local evolution is determined entirely by the local expansion of the Universe. It may be defined as the appropriately normalized perturbation of the quantity, defined using a slicing of spacetime such that the expansion between slices is spatially homogeneous. To first order, on superhorizon scales, the slicing with unperturbed intrinsic curvature has this property. A general construction is given for conserved quantities, yielding the curvature perturbation $\ensuremath{\zeta}$ as well as other more recently considered conserved perturbations. The construction may be extended to higher orders in perturbation theory and even into the non-perturbative regime.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/151a251c59a63e0e7019cceecbbead9310e4a76e

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Citations in the corpus

The exponential tail of inflationary fluctuations: consequences for primordial black holes (2019, background): “This is known as the “quasiisotropic” [70–73] or “separate universe” approach [66, 74, 75], the validity of which has recently been shown to extend beyond slow roll [76].”
Non-Gaussianities in multi-field inflation (2006, background): “Note that ζ is conserved on large scales in simple models, even beyond linear order [25, 26].”
Quantum diffusion during inflation and primordial black holes (2017, background): “This assumption is known as the “quasi-isotropic” [45–48] or “separate universe” approach [41, 49, 50], and allows us to neglect spatial gradients on super-Hubble scales.”
Correlation functions in stochastic inflation (2015, methodology): “Thus we can use the homogeneous FLRW solutions to describe the local evolution, which is known as the “quasiisotropic” [55–58] or “separate universe” approach [51,59, 60].”