The primordial "f_NL" non-Gaussianity, and perturbations beyond the present horizon

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Kim, Jaiseung
Naselsky, Pavel
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We show a primordial non-linear "f_NL" term may produce unphysically large CMB anisotropy for a red-tilted primordial power spectrum (n<1), because of coupling to primordial fluctuation on the largest scale. We consider a primordial power spectrum models of a running spectral index, and a transition at very low wavenumbers. We find that only negative running spectral index models are allowed, provided that there is no transition at a low wavenumbers (i.e. k<<1). For models of a constant spectral index, we find log(k_c/k_0)> -184, at 1 sigma level, on the transition scale of sharp cut-off models, using recent CMB and SDSS data.
Comment: v2: Journal information added
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Astrophysics - Cosmology and Nongalactic Astrophysics
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