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End date: 2012Subject: search.filters.subject.Gauss-Bonnet

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    Unifying Brane World Inflation with Quintessence
    (2011-07-06) Sami, M.; Dadhich, Naresh
    We review the recent attempts of unifying inflation with quintessence. It appears natural to join the two ends in the framework of brane world cosmology. The models of quintessential inflation belong to the class of non-oscillatory models for which the mechanism of conventional reheating does not work. Reheating through gravitational particle production is inefficient and leads to the excessive production of relic gravity waves which results in the violation of nucleosynthesis constraint. The mechanism of instant preheating is quite efficient and is suitable for brane world quintessential inflation. The model is shown to be free from the problem of excessive production of gravity waves. The prospects of Gauss-Bonnet brane world inflation are also briefly indicated.
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    Cosmological perturbations from brane inflation with a Gauss-Bonnet term
    (2011-07-06) Dufaux, Jean-Francois; Lidsey, James E.; Roy, Maartens
    Braneworld inflation is a phenomenology related to string theory that describes high-energy mod- ifications to general relativistic inflation. The observable universe is a braneworld embedded in 5-dimensional anti de Sitter spacetime. When the 5-dimensional action is Einstein-Hilbert, we have a Randall-Sundrum type braneworld. The amplitude of tensor and scalar perturbations from in- flation is strongly increased relative to the standard results, although the ratio of tensor to scalar amplitudes still obeys the standard consistency relation. If a Gauss-Bonnet term is included in the action, as a high-energy correction motivated by string theory, we show that there are important changes to the Randall-Sundrum case. We give an exact analysis of the tensor perturbations. They satisfy the same wave equation and have the same spectrum as in the Randall-Sundrum case, but the Gauss-Bonnet change to the junction conditions leads to a modified amplitude of gravitational waves. The amplitude is no longer monotonically increasing with energy scale, but decreases asymp- totically after an initial rise above the standard level. Using an approximation that neglects bulk effects, we show that the amplitude of scalar perturbations has a qualitatively similar behaviour to the tensor amplitude. In addition, the tensor to scalar ratio breaks the standard consistency relation.