Cosmological perturbations in the early universe

Journal Article · Sat Oct 15 04:00:00 EDT 1983 · Phys. Rev. D; (United States)

DOI:https://doi.org/10.1103/PhysRevD.28.1809· OSTI ID:5471080

Brandenberger, R; Kahn, R; Press, W H

We elucidate and somewhat extend Bardeen's gauge-invariant formalism for calculating the growth of linear gravitational perturbations in a Friedmann-Robertson-Walker cosmological background. We show that the formalism can be derived from the usual gravitational Lagrangian, by variation with respect to a restricted set of metric perturbation functions. This approach produces a natural decomposition of an arbitrary matter field (whose constitutive equations need not resemble the usual cosmological perfect fluid) into a spatially homogeneous piece, which couples to the background metric, plus a spatially inhomogeneous piece, which is not necessarily small and which is the source term in a second-order differential equation which evolves the gauge-invariant metric perturbation potential. We show how the complete perturbed metric can be reconstructed in arbitrary gauge from the single gauge-independent metric potential, so that the evolution of the matter fields can be concurrently calculated in the usual manner (i.e., in a perturbed coordinate frame). The approach of this paper is designed to be particularly suited to the study of fluctuations generated by classical scalar or gauge fields in ''inflationary'' cosmological models.

• Research Organization: Department of Physics, Harvard University, Cambridge, Massachusetts 02138 and Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138
• OSTI ID: 5471080
• Journal Information: Phys. Rev. D; (United States), Journal Name: Phys. Rev. D; (United States) Vol. 28:8; ISSN PRVDA
• Country of Publication: United States
• Language: English

Related Subjects

640106* -- Astrophysics & Cosmology-- Cosmology
645400 -- High Energy Physics-- Field Theory
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
COSMOLOGICAL MODELS
FUNCTIONS
GAUGE INVARIANCE
GRAVITATIONAL FIELDS
INVARIANCE PRINCIPLES
LAGRANGIAN FUNCTION
MATHEMATICAL MODELS
METRICS
PERTURBATION THEORY
SPACE-TIME
UNIVERSE