5 research outputs found
Linear density perturbations in multifield coupled quintessence
18 pages, 8 figures, version to be submitted to PRD, refs. added19 pages, 9 figures, version accepted for publication by PRD, refs. added, extra Consistency Test section added19 pages, 9 figures, version accepted for publication by PRD, refs. added, extra Consistency Test section adde
Vector and tensor contributions to the curvature perturbation at second order
We derive the evolution equation for the second order curvature perturbation
using standard techniques of cosmological perturbation theory. We do this for
different definitions of the gauge invariant curvature perturbation, arising
from different splits of the spatial metric, and compare the expressions. The
results are valid at all scales and include all contributions from scalar,
vector and tensor perturbations, as well as anisotropic stress, with all our
results written purely in terms of gauge invariant quantities. Taking the
large-scale approximation, we find that a conserved quantity exists only if, in
addition to the non-adiabatic pressure, the transverse traceless part of the
anisotropic stress tensor is also negligible. We also find that the version of
the gauge invariant curvature perturbation which is exactly conserved is the
one defined with the determinant of the spatial part of the inverse metric.Comment: 21 pages. Appendix added and conclusions extended. Updated to match
version published in JCA
Conserved quantities in Lemaitre-Tolman-Bondi cosmology
We study linear perturbations to a Lema{\^\i}tre-Tolman-Bondi (LTB)
background spacetime. Studying the transformation behaviour of the
perturbations under gauge transformations, we construct gauge invariant
quantities. We show, using the perturbed energy conservation equation, that
there are conserved quantities in LTB, in particular a spatial metric trace
perturbation, \zeta_{SMTP}, which is conserved on all scales. We then briefly
extend our discussion to the Lema{\^\i}tre spacetime, and construct
gauge-invariant perturbations in this extension of LTB spacetime.Comment: 16 pages, 0 figures, revtex4; v5: minor changes, additional 2+2
formalism appendix added, references added, version accepted by CQ