content_image/298371.jpg content_image/298368.jpg content_image/298369.jpg
<img src='content_image/298371.jpg'>

In order to obtain the power spectrum, note that the improved form of G ( t ) (6) quickly approaches to G$_{0}$ for larger times, and thus can be considered constant after inflation and in the radiation and matter dominated era. This means that the non–improved growth of perturbations works also in this case and the transfer function has not any improvement and is given by the standard one [18]. Therefore the power spectrum is given by: 

<img src='content_image/298368.jpg'>

where T is the transfer function [18], κ = √ 2 q/q$_{EQ}$ , q$_{EQ}$ ≃ Ω$_{M}$ h $^{2}$/ 13 . 6Mpc (with Ω$_{M}$ the matter density parameter, and H = h × 100km/sec Mpc) is the exit wave number at radiation–matter equality time, and 

<img src='content_image/298369.jpg'>

The result is plotted in figure (3) and the improved power spectrum is compared with the non–improved one. 

