Tachyon warm-logamediate inflationary universe model in a high dissipative regime

Abstract

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}.