Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-09-05
Phys.Rev.D73:043505,2006
Astronomy and Astrophysics
Astrophysics
25 pages, 3 figures, 1 table, submitted to Phys. Rev. D
Scientific paper
10.1103/PhysRevD.73.043505
Recent second-order perturbation computations have provided an accurate prediction for the primordial gravitational potential $\Phi(x)$ in scenarios in which cosmological perturbations are generated either during or after inflation. This enables us to make realistic predictions for a non-Gaussian part of $\Phi(x)$, which is generically written in momentum space as a double convolution of its Gaussian part with a suitable kernel, f_NL(k1,k2). This kernel defines the amplitude and angular structure of the non-Gaussian signals and originates from the evolution of second-order perturbations after the generation of the curvature perturbation. We derive a generic formula for the CMB angular bispectrum with arbitrary f_NL(k1,k2) and examine the detectability of the primordial non-Gaussian signals from various scenarios such as single-field inflation, inhomogeneous reheating, and curvaton scenarios. Our results show that in the standard slow-roll inflation scenario the signal actually comes from the momentum-dependent part of f_NL(k1,k2), and thus it is important to include the momentum dependence in the data analysis. In the other scenarios the primordial non-Gaussianity is comparable to or larger than these post-inflationary effects. We find that WMAP cannot detect non-Gaussian signals generated by these models. Numerical calculations for l>500 are still computationally expensive, and we are not yet able to extend our calculations to Planck's angular resolution; however, there is an encouraging trend which shows that Planck may be able to detect these non-Gaussian signals.
Hansen Frode K.
Komatsu Eiichiro
Liguori Michele
Matarrese Sabino
Riotto Antonio
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