Gaugeinvariant Joining Conditions for Cosmological Perturbations
Abstract
Two independent gaugeinvariant variables which are continuous at any transition where there is a discontinuous change in pressure are derived. This is valid on any scale and for a general background, subject only to the assumption that the contents of the universe are a perfect fluid. Separately, the continuous variables for a transition from one scalar field to another are shown. The physical significance of these variables are discussed and compared with other, previously suggested, joining conditions. The evolution of largescale cosmological perturbations is examined, assuming that the pressure is a function only of energy density, together with these joining conditions. It is noted that in inflationary models it is not necessary to consider the evolution of the universe between the time a perturbation expands beyond the Hubble horizon, and the time it comes within the horizon again to predict the final amplitude of the fluctuations.
 Publication:

The Astrophysical Journal
 Pub Date:
 December 1991
 DOI:
 10.1086/170726
 Bibcode:
 1991ApJ...382..363H
 Keywords:

 Computational Astrophysics;
 Cosmology;
 Perturbation Theory;
 Universe;
 Astronomical Models;
 Equations Of State;
 Galactic Evolution;
 Power Spectra;
 Astrophysics;
 COSMOLOGY;
 GALAXIES: FORMATION;
 RELATIVITY