Perturbation theory in nonstandard cosmology

TL;DR

This paper investigates inhomogeneous perturbations in nonstandard cosmology using a Schwarzschild solution mapping, revealing solutions with finite energy density but zero pressure.

Contribution

It introduces a method to analyze perturbations in nonstandard cosmology through a Schwarzschild mapping, providing explicit solutions.

Findings

Finite energy density achieved in perturbations

Pressure must be zero in the solutions

Perturbation equations solvable by power series

Abstract

We study inhomogeneous perturbations away from the strongly homogeneous background cosmology previously studied. The problem is greatly simplified by using the mapping on the inner Schwarzschild solution. The resulting linear perturbation equations can be solved by power series. The solution leads to a finite energy density, but the pressure must be zero.