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A new approach to the evolution of cosmological perturbations on large scales

David Wands·Karim A. Malik·David H. Lyth·Andrew R. Liddle
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Abstract

We discuss the evolution of linear perturbations about a Friedmann-Robertson-Walker background metric, using only the local conservation of energy-momentum. We show that on sufficiently large scales the curvature perturbation on spatial hypersurfaces of uniform-density is conserved when the non-adiabatic pressure perturbation is negligible. This is the first time that this result has been demonstrated independently of the gravitational field equations. A physical picture of long-wavelength perturbations as being composed of separate Robertson-Walker universes gives a simple understanding of the possible evolution of the curvature perturbation, in particular clarifying the conditions under which super-horizon curvature perturbations may vary.

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David Wands, Karim A. Malik, David H. Lyth, Andrew R. Liddle. 2000-06-02. A new approach to the evolution of cosmological perturbations on large scales. https://doi.org/10.1103/physrevd.62.043527

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