Accelerated expansion of the universe in a non-trivial extra-dimensional topology

Abstract

The recent observational available data for an accelerated expansion state of the present universe, obtained from distant SNeIa gave strong support to the search of alternative cosmologies. Recently, there have been a number of different attempts to modify Einstein's gravity to yield accelerated expansion at late times. Unfortunately, many of the theoretical models discussed in the literature are plagued with theoretical problems, in particular the singularity problem at the origin of time. In the present work we have analyzed a multidimensional spacetime Friedmann-RobertsonWalker (FRW) model with a decaying cosmological constant and a varying gravitational constant. Many interesting consequences are revealed, in particular the behavior of the scale factor and the shape of the universe in terms of the number of extra dimensions.Keywords Higher-dimensional cosmology · Decaying lambda · Dark energy · Phantom energy PACS 04.50.+h · 11.25.Yb · 98.80.Es · 95.36.+xThe recent available astronomical observations (around 1998 and 1999) of the dynamics of galaxies, cluster of galaxies, of luminosity distances of the Type Ia supernovae (SNeIa) as a function of redshift with redshift in the range −0.10 ≤ z ≤ 0.83, the first acoustic peak of the CMB temperature fluctuations or anisotropies and also the observational results coming from the cosmic microwave background radiation along with the Maxima and Boomerang data favor a spatially flat matter dominated universe undergoing a phase of accelerated expansion dominated by an unknown form of repulsive energy dubbed "Dark Energy (DE)". This ephemeral dark energy should have a negative pressure and has special effects that have only been detected on the largest scales of our Universe and then only in the past ten years (Riess et al. 1998;Perlmutter et al. 1999;Schmidt et al. 1998;Steinhardt et al. 1999;Persic et al. 1996;Carmeli and Kuzmenko 2002;Behar and Carmeli 2002). Presently, as already mentioned, the universe is accelerating in time with the equation of state (EoS) parameter w = p/ρ < −1/3 (ρ and p are respectively the density and pressure of a perfect fluid). However, for models described by w > −1, the null energy condition T μν k μ k ν > 0 is satisfied (T μν is the stress-energy tensor for all time-like vectors k μ ). In contrast to models with w < −1 (phantom energy), the null energy condition ρ + p < 0 with ρ > 0 is violated. Surprisingly, this case is not excluded by observation.In fact, the observed DE is dominated by some fields that have not yet relaxed to their vacuum state. Questions still linger about the nature of dark matter, especially its distribution in the central region of clusters and galaxies. The nature of the dark energy component responsible for the accelerated expansion of the universe is one of the most profound problems in high energy physics. On the other hand the results of large-scale structure surveys and the results of measurements of the masses of galaxies give a best fit for the density parameter for matter of m,0 = 0.3 and consequently ...

Noncommutative accelerated multidimensional universe dominated by quintessence

“…Within the structure of extra dimensions, the decaying of the effective cosmological constant plays a fundamental role (Darabi 2003;Mersini 2001;Koyama 2008). Various ansatzes of the decaying lambda have been explored in cosmology, which exhibit crucial roles in higherdimensional cosmology (El-Nabulsi 2009a, 2009b, 2009c, 2009d and wormhole physics (El-Nabulsi 2009e, 2009f, 2009g). In this work, our main aim is to derive the time dependence of the cosmological constant from the theory itself.…”

“…There are, of course, other phenomenologically interesting models which predict a simultaneous time variation G and lambda, e.g. non-minimal coupling theories (El-Nabulsi 2009b, 2009c, 2009d among others. By varying the field equation (2) with respect to the metric, we obtain the Friedmann equation…”

10-dimensional cosmology with Gauss-Bonnet gravity in generalized scalar-tensor theories from superstring theories

“…without the presence of phantom field of any kind and independent of the signature of the GB coupling parameter. There exist other specific scenarios of dark energy with striking features capable of explaining the present accelerated expansion of the universe [40,41,42,43,44,45]. The simple model described in this paper belongs to the same sort but holds some new features discussed above.…”

Accelerated expansion of an anisotropic Brans–Dicke cosmology from nonlinear derivative interaction and Gauss–Bonnet invariant

“…The additional scalar field ψmay be identified to dark matter field. Our thought is in fact based on recent study of scalar-tensor cosmology applied for dark energy description [19][20][21][22][23][24][25][26][27][28][29]. It is noteworthy that during the transition from non-phantom phase to phantom phase, the instability of the one scalar model becomes infinite at the transition point [30].…”