The CMB modulation from inflation

Erickcek, Kamionkowski and Carroll proposed in 2008 that the dipole modulation of the CMB could be due to a very large scale perturbation of the field phi causing the primordial curvature perturbation. We repeat their calculation using weaker assumptions and the current data. If phi is the inflaton of any single-field inflation with the attractor behaviour, the asymmetry is almost certainly too small. If instead phi is any curvaton-type field (ie. one with the canonical kinetic term and a negligible effect during inflation) the asymmetry can agree with observation if vertical bar f(NL)vertical bar in the equilateral configuration is similar or equal to 10 for k(-1) = 1 Gpc and less than or similar to 3 for k(-1) = 1 Mpc. An f(NL) with these properties can apparently be obtained from the curvaton with an axiom( potential. Within any specific curvaton-type model, the function f(NL) (k(1) k(2), k(3)) required to generate the asymrnetry would be determined, and could perhaps already be confirmed or ruled out using existing Planck or WMAP data.