.. they have not considered any other possible reasons for a red shift to occur other than a Doppler effect. ....
By the Aether Wave theory
(AWT) and gravastar
theory the Universe if formed by the interior of sort black hole, which collapses by its gravity, thus increasing its density. From the point of view the internal observer, which is formed by the standing waves of such interior, such collapse is perceived as the space expansion (you can click to the animation below to see the AVI video at better resolution)
How the dark matter has appeared? By the AWT
, the vacuum is foamy massive environment, which is the result of phase transform. The very similar process appears during condensation of so called supercritical vapor, during this the intimate mixture less and more dense phase appears, similar to foam. Such foam is heavy, so it induces a further phase transition in spherically growing zones like crystalline aggregates fast growing from over-saturated solution.
Whenever such spherical zones met together, an immense collapse occurs, which will lead into formation of globules of heavily compressed hot matter, so called quasars. After leveling of pressure and establishing of equilibrium, the most of quasars matter is radiated back again into vacuum, where it forms an interstellar gas, the source of galaxy material. The more massive vacuum, the energy of which isn't able to form a particles of observable matter is forming an invisible dark matter streaks. The dark matter is composed from cool part and hot part, the later one it can contain some very heavy particles or highly ionized atom nuclei. The cool part can contain gravitophotons. neutrinos or some primordial ultra-lightweight particles, like axions and neutralinos. The quasars after cooling and radiating of excessive matter are forming a black holes residues at the centers of most of newly created galaxies.