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Register a new userChaplygin gas braneworld inflation according to WMAP7 data
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We consider a Chaplygin gas model with an exponential potential in framework of braneworld inflation. We apply the slow-roll approximation in the high-energy limit to derive various inflationary spectrum perturbation parameters. We show that the inflation observables depend only on the e-folding number N and the final value of the slow-roll parameter e(end). Whereas for small running of the scalar spectral index dns/dlnk, the inflation observables are in good agreement with recent WMAP7 data.
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We are interested on studing various inflationary spectrum perturbation parameters in the context of the Randall-Sandrum type 2 Braneworld model. We consider in particular three types of potentials. We apply the slow-roll approximation in the high energy limit to constraint the parameter potentials by confronting our results to recent WMAP7 observations. We show that, for some values of the e-folding number N; the monomial potential provides the best fit results to observations data.
Positively-curved, oscillatory universes have recently been shown to have important consequences for the pre-inflationary dynamics of the early universe. In particular, they may allow a self-interacting scalar field to climb up its potential during a very large number of these cycles. The cycles are naturally broken when the potential reaches a critical value and the universe begins to inflate, thereby providing a `graceful entrance to early universe inflation. We study the dynamics of this behaviour within the context of braneworld scenarios which exhibit a bounce from a collapsing phase to an expanding one. The dynamics can be understood by studying a general class of braneworld models that are sourced by a scalar field with a constant potential. Within this context, we determine the conditions a given model must satisfy for a graceful entrance to be possible in principle. We consider the bouncing braneworld model proposed by Shtanov and Sahni and show that it exhibits the features needed to realise a graceful entrance to inflation for a wide region of parameter space.
In this paper we study the Chaplygin gas model as a candidate for inflation in the framework of the Randall Sundrum type-II braneworld model. We consider the original and generalized Chaplygin gas model in the presence of monomial potential. The inflationary spectrum perturbation parameters are reformulated and evaluated in the high-energy limit and we found that they depend on several parameters. We also showed that these perturbation parameters are widely compatible with the recent Planck data for a particular choice of the parameters space of the model. A suitable observational central value of $n_{s}simeq $ $0.965$ is also obtained in the case of original and generalized Chaplygin gas.
Braneworld inflation is a phenomenology related to string theory that describes high-energy modifications to general relativistic inflation. The observable universe is a braneworld embedded in 5-dimensional anti de Sitter spacetime. Whe the 5-dimensional action is Einstein-Hilbert, we have a Randall-Sundrum type braneworld. The amplitude of tensor and scalar perturbations from inflation 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 asymptotically 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.
We investigate early time inflationary scenarios in an Universe filled with a dilute noncommutative bosonic gas at high temperature. A noncommutative bosonic gas is a gas composed of bosonic scalar field with noncommutative field space on a commutative spacetime. Such noncommutative field theories was recently introduced as a generalization of quantum mechanics on a noncommutative spacetime. As key features of these theories are Lorentz invariance violation and CPT violation. In the present study we use a noncommutative bosonic field theory that besides the noncommutative parameter $theta$ shows up a further parameter $sigma$. This parameter $sigma$ controls the range of the noncommutativity and acts as a regulator for the theory. Both parameters play a key role in the modified dispersion relations of the noncommutative bosonic field, leading to possible striking consequences for phenomenology. In this work we obtain an equation of state $p=omega(sigma,theta;beta)rho$ for the noncommutative bosonic gas relating pressure $p$ and energy density $rho$, in the limit of high temperature. We analyse possible behaviours for this gas parameters $sigma$, $theta$ and $beta$, so that $-1leqomega<-1/3$, which is the region where the Universe enters an accelerated phase.
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