New inflation versus chaotic inflation, higher degree potentials, and the reconstruction program in light of WMAP 3-year data

The cosmic microwave background 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/dln⁡k) on the degree of the potential (2n) 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 yields 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/dln⁡k≤-2×10^-4. (The values of r, n_s, dn_s/dln⁡k for arbitrary N_e follow by a simple rescaling from the N_e=50 values.) A reconstruction program is carried out suggesting quite generally that for n_s consistent with the WMAP3 and LSS data and r<0.1 the symmetry breaking scale for new inflation is |ϕ₀|∼10M_Pl while the field scale at Hubble crossing is |ϕ_c|∼M_Pl. The family of chaotic models features 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/dln⁡k with a narrow window in field amplitude around |ϕ_c|∼15M_Pl. We conclude that a measurement of r<0.16 (for N_e=50) distinctly rules out a large class of chaotic scenarios and favors small field new inflationary models. As a general consequence, new inflation emerges more favored than chaotic inflation.