Quintessence cosmology with a traversable wormhole, massive decaying gravitons and with varying G and Λ

Abstract

In this work, we explore many cosmological implications of a four-dimensional cosmology dominated by quintessence with a static traversable wormhole, spatiotemporal varying G and by taking into account a decaying cosmological constant and a decaying graviton mass by means of an additional bimetric tensor in Einstein's field equations proposed by Visser in 1998.The recent astronomical observations indicate that our universe is dominated by dark matter and dark energy with abundances exceedingly tuned to baryonic matter. These findings suggest that Einstein's general relativity requires a modification in particular at large cosmological scale and in particular due to the observed discrepancy between luminous and gravitational masses (Tegmark 2004). Broadly speaking, in modified theories of gravity, the graviton particle is massless. In fact, the essential property that guarantees masslessness of the graviton is invariance under diffeomorphisms (Chamseddine 2004). It was recently argued that the inverse graviton mass can be not only considerably smaller than the current size of the universe, but also many orders of magnitude slighter than the galactic scales. Furthermore, A.R. El-Nabulsi ( )

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].…”

Dark energy from “extended modified gravity” and Gauss–Bonnet invariant term

“…However, it has been long expected that a better understanding of modern cosmology needs to include higherorder curvature derivative term (modified gravity) Odintsov 2006, 2007;El-Nabulsi 2009c, 2009d, 2010c, 2010dDas and Banerjee 2008). The so-called f (R) theories of gravity have been recently receiving special awareness due to the opportunity they open to account for the late-time accelerated expansion without the need to include any explicit extra degrees of freedom.…”