Modified Brans-Dicke scalar tensor theories with generalized stringy Gauss-Bonnet corrections

Abstract

We explore the late-time dynamics of a fourdimensional homogeneous and isotropic universe based on a modified Brans-Dicke scalar tensor theory in the presence of string corrections and Gauss-Bonnet curvature corrections. Many original and attractive cosmological features are revealed and discussed in some details.Keywords Modified Brans-Dicke cosmology · String corrections · Gauss-Bonnet invariant term · Accelerated expansionThe analysis of the three year WMAP observations data and the very recent one of the five-year WMAP data from Supernova Legacy Survey of type Ia and galaxy indicate that our universe is accelerating with time and is governed by a mysterious form of dark energy (DE) with negative pressure obeying the equation of state parameter (EoSP) −1.14 < w < −0.93 at 68% confidence level (Riess et al. 1998(Riess et al. , 2004. Furthermore, the observational sets suggest that the Universe is spatially flat as predicted by the inflationary scenario with k = −0.015 +0.020 −0.016 within the limits of observational accuracy based on Gaussianity and adiabaticity of the CMBR power spectrum (Riess et al. 1998(Riess et al. , 2004Perlmutter et al. 1999;Schmidt et al. 1998;Steinhardt et al. 1999;Persic et al. 1996;Cunha 2009). The distribution of energy in the universe is roughly 76% DE, 20% dark matter (DM) and only 4% baryonic matter (BM). However, distance measurement from SNIa and Baryon Acoustic Oscillation confirms the presence of 73% of dark energy together with the range of the equation of state parameter −1.33 < w < −0.79. At first sight, a positive cosmological constant seems to fit correctly the observational data, but unfortunately, including a cosmological constant in the field equations come with a price: the lambda constant problem as well as the well-known coincidence problem.In the last few years, much work has been done and several theories were constructed in order to explain this amazing scenario that could fit correctly the CMBR as well as LSS and supernovae observations. The already build models range from the simple phenomenological Cold Dark Matter model consisting a mixture of cosmological constant and cold dark matter (CDM) which must be relics of a grand unified phase of the universe to Chaplygin gas (Fabris et al. 2002), Generalized Chaplygin gas model (Bento et al. 2002), quintom model (Feng 2006 Zhang 2006), hessence (Wei et al. 2005), holographic DE scenario (Zhao 2007), dark matter-dark energy interaction and so on (ElNabulsi 2009a and references therein). However, there has been several attempts for building alternative theories motivated from non-minimal and minimal scalar tensor theories (El-Nabulsi , string and superstring theories, in particular, the GaussBonnet gravity theory, models with higher-order curvature terms (El-Nabulsi

Late Time Acceleration in Scalar-Tensor Theory with GB Interaction

“…The Gauss Bonnet interaction in the Jordan Brans-Dicke scalar tensor theory have not yet been explored in general. So far in our knowledge [42,43] provides some solution, so we consider some simple prescription to obtain the evolution of the universe. Introduction of the GB term dynamically coupled with the scalar field in the Jordan Brans Dicke theory in spatially flat, homogeneous and isotropic space-time in 4-dimension yields a transition from decelerated to late time accelerated expansion of the universe.…”

“…The scalar-Einstein Gauss Bonnet gravity have been investigated [30][31][32][33][34][35][36][37][38][39][40][41] extensively in the literature, however the GB interaction in the generalized scalar-tensor theory (or in the Jorden Brans-Dicke theory ) have not yet been explored except a few, viz. [42,43].…”

FRW models with particle creation in Brans-Dicke theory

“…Berman (2008) has discussed the shear and vorticity in an accelerating BD lambda-universe with torsion. El-Nabulsi (2010a, 2010b have investigated the Gauss-Bonnet corrections in modified BD theory and discussed their findings in detail.…”