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High Energy Physics - Theory, hep-th,Astrophysics, Cosmology and Extragalactic Astrophysics, astro-ph.CO
Abstract:
We discuss the effect of superimposing multiple sources of resonant
non-Gaussianity, which arise for instance in models of axion inflation. The
resulting sum of oscillating shape contributions can be used to "Fourier
synthesize" different non-oscillating shapes in the bispectrum. As an example
we reproduce an approximately equilateral shape from the superposition of
${\cal O}(10)$ oscillatory contributions with resonant shape. This implies a
possible degeneracy between the equilateral-type non-Gaussianity typical of
models with non-canonical kinetic terms, such as DBI inflation, and an
equilateral-type shape arising from a superposition of resonant-type
contributions in theories with canonical kinetic terms. The absence of
oscillations in the 2-point function together with the structure of the
resonant $N$-point functions, imply that detection of equilateral
non-Gaussianity at a level greater than the PLANCK sensitivity of
$f_{NL}\sim{\cal O}(5)$ will rule out a resonant origin. We comment on the
questions arising from possible embeddings of this idea in a string theory
setting.
