  Slow-roll inflation is studied as an effective field theory.We find as
consistent form of the inflaton potential V(phi)=N M^4 w(phi/[sqrt{N}M_P])
where phi is the inflaton field, M the inflation energy scale, M_P the Planck
mass, and N~50 the number of efolds since the relevant modes exited the horizon
till the end of inflation. The dimensionless function w(chi) and field chi are
O(1). The WMAP value for the amplitude of scalar adiabatic fluctuations
|\Delta_{k ad}^(S)| fixes the inflation scale M ~ 0.77 10^16 GeV precisely at
the GUT scale. This general form of the potential makes manifest that the slow
roll expansion is an expansion in 1/N. Powers of 1/N count the orders in the
slow roll expansion.This form of the inflaton potential suggests that the super
symmetry breaking scale is at the inflation and GUT scales.A Ginzburg-Landau
realization of this inflaton potential reveals that Hubble, inflaton mass and
non-linear couplings are of the see-saw form in terms of the small ratio M/M_P.
For example, the quartic coupling lambda ~ 1/N (M/M_P)^4.The smallness of the
non-linear couplings is not a result of fine tuning but a natural consequence
of the validity of the effective field theory. We clarify the Lyth bound which
relates the tensor/scalar ratio and the value of phi/M_P.Effective field theory
is valid for V(phi)<<M_P^4 allowing inflaton fields phi well beyond M_P.Thus,
no bounds based on the value of phi/M_P appear on r.In case one wishes to
restrict oneself to chi < 1 in the above potential, values for r larger than
the previous bounds are allowed thanks to the new factor sqrt{N}~7.Finally,it
is conjectured that inflation is hovering near a trivial gaussian infrared
fixed point during slow roll. Slow-roll inflation would then enjoy universality
properties as those of critical phenomena.
