ACDM cosmology with a quiescent anisotropy in a higher dimensional steady state universe

Abstract

In this work, which follows a series of studies on the higher-dimensional steady state universe idea and prepared for Professor Tekin Dereli's Festschrift, we show the infuence of the dynamical internal (unobservable) space on the evolution of the possible anisotropy of the external (observable) space. We obtain mathematically exactly the same Friedmann equation of the standard ?CDM model for the external space, but with some remarkable physical diferences. In particular, the higher-dimensional negative cosmological constant plays the role of the four-dimensional positive cosmological constant and the expansion anisotropy, viz., the shear scalar, of the external space mimics a negative cosmological constant; it would mimic a stif fuid when allowed on top of the standard ?CDM model. This latter feature gives us the opportunity to manipulate the CMB quadrupole temperature fuctuation, suggesting a possible answer to the fact that its observed value is lower than that predicted by the standard ?CDM model. © 2021 Published under licence by IOP Publishing Ltd.