Predictions of single field inflation for the tensor/scalar ratio and the running spectral index

We study the single field slow-roll inflation models that better agree with the available CMB and LSS data including the three years WMAP data: new inflation and hybrid inflation. We study these models as effective field theories in the Ginsburg-Landau context: a trinomial potential turns out to be a simple and well motivated model. The spectral index n(s) of the adiabatic fluctuations, the ratio r of tensor to scalar fluctuations and the running index dn(s)/dlnk are studied in detail. We derive explicit formulas for n(s), r and dn(s)/dlnk and provide relevant plots. In new inflation, and for the chosen central value n(s)=0.95, we predict 0.03 < r < 0.04 and -0.000 70 < dn(s)/dlnk <-0.000 55. In hybrid inflation, and for n(s)=0.95, we predict r similar or equal to 0.2 and dn(s)/dlnk similar or equal to-0.001. Interestingly enough, we find that in new inflation n(s) is bounded from above by n(s max)=0.961 528... and that r is a two valued function of n(s) in the interval 0.96 < n(s)< n(s max). In the first branch we find r < r(max)=0.114 769.... In hybrid inflation we find a critical value mu(2)(0 crit) for the mass parameter mu(2)(0) of the field sigma coupled to the inflaton. For mu(2)(0) 1 behavior. Hybrid inflation for mu(2)(0)>Lambda M-0(Pl)2/192 fulfills all the present CMB+LSS data for a large enough initial inflaton amplitude. Even if chaotic inflation predicts n(s) values compatible with the data, chaotic inflation is disfavored since it predicts a too high value r similar or equal to 0.27 for the ratio of tensor to scalar fluctuations. The model which best agrees with the current data and which best prepares the way to the expected data r less than or similar to 0.1, is the trinomial potential with negative mass term: new inflation.