1106.0627 (P. G. Miedema)

Cosmological Perturbation Theory and the Evolution of Small-Scale
Inhomogeneities    [PDF]

P. G. Miedema

It is shown that a first-order cosmological perturbation theory for the open,
flat and closed Friedmann-Lemaitre-Robertson-Walker universes admits one, and
only one, gauge-invariant variable which describes the perturbation to the
energy density and which becomes equal to the usual Newtonian energy density in
the non-relativistic limit. The same holds true for the perturbation to the
particle number density. Using these two new variables, a new manifestly
covariant and gauge-invariant cosmological perturbation theory based on the
Lifshitz-Khalatnikov theory has been developed. Perturbations in the total
energy density are gravitationally coupled to perturbations in the particle
number density, irrespective of the nature of the particles. There is, in
first-order, no back-reaction of perturbations to the global expansion of the
universe. Small-scale perturbations in the radiation-dominated era oscillate
with an increasing amplitude. Density perturbations evolve diabatically, i.e.,
they exchange heat with their environment. This heat loss of a perturbation may
enhance the growth rate of its mass sufficiently to explain stellar formation,
a phenomenon not understood, as yet, without the additional assumption of the
existence of Cold Dark Matter. This theoretical observation is the main result
of this article.

View original: http://arxiv.org/abs/1106.0627