New Inflation vs. Chaotic Inflation, Higher Degree Potentials and the Reconstruction Program in light of WMAP3

Abstract

The CMB power spectra are studied for different families of single field new and chaotic inflation models in the effective field theory approach to inflation. We implement a systematic expansion in 1/N_e where N_e ~ 50 is the number of e-folds before the end of inflation. We study the dependence of the observables (n_s, r and dn_s/d\ln k) on the degree of the potential (2 n) and confront them to the WMAP3 and large scale structure data: this shows in general that fourth degree potentials (n=2) provide the best fit to the data; the window of consistency with the WMAP3 and LSS data narrows for growing n. New inflation models yield a good fit to the r and n_s data in a wide range of field and parameter space. Small field inflation yields r<0.16 while large field inflation yields r>0.16 (for N_e=50). All members of the new inflation family predict a small but negative running -4(n+1)10^{-4}< dn_s/d\ln k <-2 10^{-4}. A reconstruction program is carried out suggesting quite generallythat for n_s consistent with the WMAP3 and LSS data and r<0.1 the symmetry breaking scale for new inflation is |ϕ_0| ~ 10 M_{Pl} while the field scale at Hubble crossing is |ϕ_{50}| ~ M_{Pl}.The family of chaotic models feature r>0.16 (for N_e=50) and only a restricted subset of chaotic models are consistent with the combined WMAP3 bounds on r, n_s,dn_s/d\ln k with a narrow window in field amplitude around |ϕ_{50}| ~ 15 M_{Pl}.A measurement of r<0.16 (for N_e =50) will distinctly rule out a large class of chaotic scenarios and will favor new inflationary models. As a general consequence, new inflation emerges more favoured than chaotic inflation.