Perturbations in some models of tachyonic inflation

TL;DR

This paper investigates a tachyonic inflation model, analyzing scalar perturbations, spectral index evolution, and non-Gaussianity, finding negligible non-Gaussian effects and consistency with standard inflation at large scales.

Contribution

It provides analytical solutions for scalar perturbations and the power spectrum in a tachyonic inflation model, including non-Gaussianity estimates, under slow-roll approximation.

Findings

Power spectrum for small k: P_ζ ~ 1/k^{0.5 + ν_2}

At large k, spectrum matches standard inflation

Non-Gaussianity parameter f_NG ≈ 0, negligible non-Gaussianities

Abstract

In the present work an inflationary tachyon field model of the early universe is considered. Several cosmological effects produced by a particular potential in this tachyonic era are studied, under the approximation of slow-roll inflation. In particular, the evolution of the spectral index $n_s$ with time is obtained. The equations for the cosmological scalar perturbations are analytically solved in order to show that the power spectrum for small $k$ values is $P_{\zeta}\sim 1/k^{\frac{1}{2}+\nu_2}$, where $\nu_2$ depends on the barotropic index $\gamma_0$. For large $k$ values we find that the power spectrum is well approximated by the standard inflation model. Additionally, the three-point correlation function is calculated in order to get the primordial non-Gaussianity of the perturbation. The result is that $f_{NG} \simeq 0$ so the non-gaussianities generated by this tachyon field are negligible.