Neil Barnaby, Sarah Shandera
Primordial non-Gaussianity is generated by interactions of the inflaton
field, either self-interactions or couplings to other sectors. These two
physically different mechanisms can lead to nearly indistinguishable bispectra
of the equilateral type, but generate distinct patterns in the relative scaling
of higher order moments. We illustrate these classes in a simple effective
field theory framework where the flatness of the inflaton potential is
protected by a softly broken shift symmetry. Since the distinctive difference
between the two classes of interactions is the scaling of the moments, we
investigate the implications for observables that depend on the series of
moments. We obtain analytic expressions for the Minkowski functionals and the
halo mass function for an arbitrary structure of moments, and use these to
demonstrate how different classes of interactions might be distinguished
observationally. Our analysis casts light on a number of theoretical issues, in
particular we clarify the difference between the physics that keeps the
distribution of fluctuations nearly Gaussian, and the physics that keeps the
calculation under control.
View original:
http://arxiv.org/abs/1109.2985
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