Generating $\fnl$ at $\ell\lsim 60$

Abstract

The CMB anisotropy at $\ell\lsim 60$ seems to have some special features which include (i) a dipole modulation and (ii) a decrease in power. It is known that both of these effects can be generated if a curvaton-type field has a super-horizon perturbation. It is also known that this will generate non-gaussianity $\fnl$ in the same range of $\ell$, whose magnitude has a lower bound coming from the magnitude of the observed CMB quadrupole. I revisit that bound in the present paper, and point out that it may or may not be compatible with current data which should therefore be re-analysed.

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