Cosmological perturbations in warm-tachyon inflationary universe model with viscous pressure on the brane

We study warm-viscous inflationary universe model on the brane, in a tachyon field theory. We obtain the general conditions which are required for this model to be realizable. In longitudinal gauge, the primoradial perturbation parameters are found in great details, using slow-roll and quasi-stable approximations. The general expressions of the tensor-to-scalar ratio, scalar spectral index and its running are found. We derive the characteristics of the inflationary universe model by using an effective exponential potential in two cases: 1- Dissipative parameter $\Gamma$ and bulk viscous parameter $\zeta$ are constant parameters. 2- Dissipative parameter as a function of tachyon field $\phi$ and bulk viscous parameter as a function of radiation-matter mixture energy density $\rho$. The parameters of the model are restricted by recent observational data from the seven-year Wilkinson microwave anisotropy probe (WMAP7).Comment: 27 pages, 6 figures, accepted for publication by JHE

Cosmological New Massive Gravity and Galilean Conformal Algebra in 2-dimensions

In the present paper we consider the realization of $2-$dimensional Galilean conformal algebra ($GCA_2$) on the boundary of cosmological new massive gravity. At first we consider the contracted BTZ black hole solution. We obtain entropy formula for the $GCA_2$ in term of contracted scaling dimension $\Delta$ and central charge $C_1$. This entropy formula exactly matches with the non-relativistic limit of Bekenstein-Hawking entropy of BTZ black hole. Then we extend our study to the contracted warped $AdS_3$ black hole solution of CNMG. We obtain the entropy of dual $GCA_2$ in terms of central charges and finite temperatures, $T_1, T_2$. Again this expression coincides with the non-relativistic limit of Bekenstein-Hawking entropy formula of warped $AdS_3$ black hole.Comment: 11 pages, no figure. arXiv admin note: text overlap with arXiv:1103.0457, arXiv:1102.0082, arXiv:1101.2339, arXiv:1202.491

Tachyon Warm-Logamediate Inflationary Universe Model in High Dissipative Regime

In the present work, we study warm tachyon inflation model in the context of "logamediate inflation" where the cosmological scale factor expands as $a=a_0\exp(A[\ln t]^{\lambda})$. The characteristics of this model in slow-roll approximation are presented in two cases: 1- Dissipative parameter $\Gamma$ is a function of tachyon field $\phi$. 2- $\Gamma$ is a constant parameter. The level of non-Gaussianity of this model is found for these two cases. Scalar and tensor perturbations for this scenario are presented. The parameters appearing in our model are constrained by recent observational data (WMAP7). Harrison-Zeldovich spectrum, i.e. $n_s=1,$ is approximately obtained for large values of $\lambda$ (i.e. $\lambda\simeq 50$)and normal value of number of e-folds, i.e. $N\simeq 60$. On the other hand, the scale invariant spectrum (Harrison-Zeldovich spectrum) is given by using two parameters in our model. For intermediate inflation, where the cosmological scale factor expands as $a=a_0\exp(A t^{f}),$ this spectrum has been exactly obtained using one parameter, i.e. $f=2/3$ \cite{2-n}.Comment: 17 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:1210.074

Warm-polytropic inflationary universe model

In the present paper we study warm inflationary universe models in the context of a polytropic gas. We derive the characteristics of this model in slow-roll approximation and develop our model in two cases, 1- For a constant dissipative parameter $\Gamma$. 2- $\Gamma$ as a function of scalar field $\phi$. In these cases we will obtain exact solution for the scalar field and Hubble parameter. We will also obtain explicit expressions for the tensor-scalar ratio $R$, scalar spectrum index $n_s$ and its running $\alpha_s$, in slow-roll approximation.Comment: 13 pages, 1 figur