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 ΛCDM 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 ΛCDM 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 ΛCDM model.

Noncompactified Kaluza–Klein Gravity

“…Aside from the FLRW model [34], anisotropic cosmological models have been studied in the context of GR or the alternative theories to GR (in 4D as well as higher-dimensional contexts) [35][36][37][38][39][40], and noncompactified KK theories [12,[41][42][43]. In this paper, we presented the anisotropic BD-KS model as an application of the MBDT.…”

Hubble Tension: The Evidence of New Physics

“…In addition to the above theoretical challenges, the two main components in the ΛCDM model, dark matter (DM) and dark energy (DE), are poorly understood. Moreover, there are also some tensions between the cosmological and astrophysical observations and the ΛCDM model, which include the Hubble tension [3,[33][34][35][36][37][38][39][40] (5σ), growth tension [41][42][43] (2-3σ), CMB anisotropy anomalies [22,[44][45][46][47][48][49][50][51][52][53] (2-3σ), cosmic dipoles [23, [54][55][56][57][58][59][60][61][62][63] (2-5σ), Baryon Acoustic Oscillation (BAO) curiosities [64][65][66] (2.5-3σ), parity violating rotation of CMB linear polarization [67][68][69][70], small-scale curiosities [71][72][73][74], age of the universe [75], the Lithium problem [76] (2-4σ),the quasar Hu...…”