Construction of nonsingular pre-big-bang and ekpyrotic cosmologies and the resulting density perturbations

By S. Tsujikawa, Robert Brandenberger, F. Finelli. 2002

163 citations recorded by the source corpus.

We consider the construction of nonsingular Pre-Big-Bang and Ekpyrotic type cosmological models realized by the addition to the action of specific higher-order terms stemming from quantum corrections. We study models involving general relativity coupled to a single scalar field with a potential motivated by the Ekpyrotic scenario. We find that the inclusion of the string loop and quantum correction terms in the string frame makes it possible to obtain solutions of the variational equations which are nonsingular and bouncing in the Einstein frame, even when a negative exponential potential is present, as is the case in the Ekpyrotic scenario. We analyze the spectra of perturbations produced during the bouncing phase and find that the spectrum of curvature fluctuations in the model proposed originally to implement the Ekpyrotic scenario has a large blue tilt ($n_R= 3$). Except for instabilities introduced on small scales, the result agrees with what is obtained by imposing continuity of the induced metric and of the extrinsic curvature across a constant scalar field (up to $k^2$ corrections equal to the constant energy density) matching surface between the contracting and the expanding Einstein Universes. We also discuss nonsingular cosmological solutions obtained when a Gauss-Bonnet term with a coefficient suitably dependent on the scalar matter field is added to the action in the Einstein frame with a potential for the scalar field present.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/1ab40edeb6420969430afd085a9c232d549eedcb

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Citations in the corpus

First-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Implications For Inflation (2003, background): “Note, however, that predictions for the primordial perturbation spectrum resulting from the Ekpyrotic scenario are controversial (see, for example, Tsujikawa et al. (2002)).”
Rapidly-Varying Speed of Sound, Scale Invariance and Non-Gaussian Signatures (2008, methodology): “This has been shown to occur, for example, in the slowly contracting background of the new ekpyrotic cosmology [3, 4, 5, 6, 7, 8] or in the kinetic dominated pre-big bang cosmology [9, 10].”
Nonsingular cosmology with a scale-invariant spectrum of cosmological perturbations from Lee-Wick theory (2008, unknown): “These conclusions were confirmed in some specific models in which the bounce was smoothed out by making use of higher derivative gravity terms (see [57] in the case of the Pre-Big-Bang model and [58, 59] in the case of the Ekpyrotic scenario).”
f(R) Theories (2010, methodology): “The GB coupling in the case (i) appears in lowenergy string effective action [275] and cosmological solutions in such a theory have been studied extensively (see [34, 273, 105, 147, 588, 409, 468] for the construction of nonsingular cosmological solutions and [463, 360, 361, 593, 523, 452, 453, 381,”
The dS/CFT Correspondence and the Big Smash (2001, background): “These cosmologies are of interest not merely because of the observational data (though these [4] are certainly very suggestive) but also because the non-singular “bouncing” cosmologies which have recently attracted much attention (see [ 26 ] and its references) necessarily violate the DEC during (at”
Non-singular cosmology in a model of non-relativistic gravity (2009, background): “Recently, the scenario of oscillating universe (originally proposed by [63] and awaked later as ekpyrotic/cyclic by [64–66]), in which the universe experiences a sequence of contractions and expansions, has been widely studied in the literature, for instance in the context of loop quantum gravity [4”