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

El-Nabulsi, Ahmad Rami

doi:10.1007/s10714-010-0966-8

Cited by 10 publications

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References 35 publications

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“…In the high-curvature region, the coupling is also big. The slowing down of the inflationary rate and the end of the fast expansion rate due to bubble nucleation renders the BD theory an appealing candidate for many cosmological problems (El-Nabulsi 2010a, 2010bBrans & Dicke 1961;Veneziano 1996). However, one possible way to deal with a successful dark energy theory is to implement in the theory a dynamical dilatonic field inspired by string theories, i.e.…”

Section: Introductionmentioning

confidence: 99%

Accelerated Dilatonic-Brans-Dicke cyclic and non-singular universe from string theory

El-Nabulsi¹

2011

Res. Astron. Astrophys.

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We discuss the late-time dynamics of a particular four-dimensional Brans-Dicke cosmology with a dilaton field motivated by string theories (solitonic p-branes or D-branes) in which the dilaton field and the scale factor of the flat, homogeneous spacetime are correlated. We examine the late-time-evolution of the equations of motion where various attractive consequences are revealed and discussed in some detail.

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Section: Introductionmentioning

confidence: 99%

Accelerated Dilatonic-Brans-Dicke cyclic and non-singular universe from string theory

El-Nabulsi¹

2011

Res. Astron. Astrophys.

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“…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;Zhao and 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 2005a, 2006a, 2006b, 2009b, 2010a, 2010b, string and superstring theories, in particular, the GaussBonnet gravity theory, models with higher-order curvature terms (El-Nabulsi 2006b, 2007a, 2007b, 2008a, 2008cKao 2000), dilaton field of string theories with gaugino condensation (El-Nabulsi 2009a, 2009c, 2009d and references therein), fractional functional approach (El-Nabulsi 2007c, 2007d. It is noteworthy that higher-order curvature terms play a crucial role at high energy limits closed to the Planck epoch as well as around the Big Rip.…”

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

El-Nabulsi

2010

Astrophys Space Sci

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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

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D-Dimensional non-singular universe dominated by dark energy

El-Nabulsi

2010

Astrophys Space Sci

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We discuss the possibility that we are living in a non-singular superinflationary universe and dominated by dark energy. Motivated from superstring and M-theory, the cosmology introduced here is based on the effective action of the dilaton scalar field in the presence of the matter source term. Many novel and interesting consequences are revealed through this work and discussed in some details.Keywords Higher-dimensions · Dilaton field · Scalar field · Phantom energy · Dark energy · Superinflation Following the recent advances in sting, superstring and Mtheory, we believe that extra-dimensions really exist at very high energy limit, that is, at the Planck energy regime. However, as we are living in a four-dimensional spacetime, the extra-dimension is invisible and furthermore, we expect that the later decays in time. The recent discovery of dark energy as a theoretical explanation of the accelerated expansion of the Universe is a big unattended surprise in cosmology. In fact, the recent observations of the Type SNeIa supernovae, cosmic microwave background (CMB) anisotropies, the large scale galaxies structures of the universe and SachsWolfe effects have led to the idea that our universe undergoes accelerated expansion at the present epoch tending to a flat de-Sitter space-time as predicted by inflation theory (−1.14 < w < −0.93 at 68% confidence level and has special effects that have only been detected on the largest scales of our Universe and then only in the past ten years (Alcaniz 2004). Several theoretical models, theories and possible solutions have been proposed, but the most popular ones are the cosmological constant or vacuum energy with a constant equation of state, or a variant of it known as quintessence simulated by a slowly rolling scalar field whose energymomentum tensor is dominated by the contribution of the field potential energy which drives a period of accelerated expansion. Unfortunately, both models are encountered by the huge fine-tuning problem required for its magnitude and the coincidence problem: why does the acceleration happen around a redshift of unity, at around 10 billion years? Other leading candidates are K-essence with modified kinetic energy (Armendariz-Picon et al. ), etc. Unfortunately, we still ignore which of these models are the most viable or more realistic than the others. The largest part of these models have significant drawbacks and suffer from serious finetuning problems e.g. fine tuning of parameters for different type of potentials which model quintessence and stability of radiative corrections from the matter sector. In addition, in many of these models, time varying dark energy is expected. With no doubt, the mystery of cosmic acceleration may be the richest, with broad connections to other important questions in modern cosmology and in elementary particle physics. One more serious additional problem that occurs on most of these phenomenological theories including the standard Big Bang model is the initial singularity problem. This serious problem still persists...

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

Cited by 10 publications

References 35 publications

Accelerated Dilatonic-Brans-Dicke cyclic and non-singular universe from string theory

Accelerated Dilatonic-Brans-Dicke cyclic and non-singular universe from string theory

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

D-Dimensional non-singular universe dominated by dark energy

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