Non-Gaussianity and the Cosmic Microwave Background Anisotropies

Bartolo, N.; Matarrese, S.; Riotto, A.

doi:10.48550/arxiv.1001.3957

Cited by 30 publications

(139 citation statements)

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“…The result is valid on super-horizon scales where spatial gradients can be neglected. In this work, we do not consider secondary effects on curvature perturbations arising from late-time physics (see [47] for a review), nor the effects of possible isocurvature modes during the late universe. The quantities N a and N ab denote derivatives of the number of e-foldings along the scalar fields.…”

Section: General Resultsmentioning

confidence: 99%

Scale-dependent non-Gaussianity probes inflationary physics

Byrnes

Gerstenlauer

Nurmi

et al. 2010

J. Cosmol. Astropart. Phys.

106

136

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Abstract:We calculate the scale dependence of the bispectrum and trispectrum in (quasi) local models of non-Gaussian primordial density perturbations, and characterize this scale dependence in terms of new observable parameters. They can help to discriminate between models of inflation, since they are sensitive to properties of the inflationary physics that are not probed by the standard observables. We find consistency relations between these parameters in certain classes of models. We apply our results to a scenario of modulated reheating, showing that the scale dependence of non-Gaussianity can be significant. We also discuss the scale dependence of the bispectrum and trispectrum, in cases where one varies the shape as well as the overall scale of the figure under consideration. We conclude providing a formulation of the curvature perturbation in real space, which generalises the standard local form by dropping the assumption that f NL and g NL are constants.

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Section: General Resultsmentioning

confidence: 99%

Scale-dependent non-Gaussianity probes inflationary physics

Byrnes

Gerstenlauer

Nurmi

et al. 2010

J. Cosmol. Astropart. Phys.

106

136

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“…The limiting cases (shapes) are known as the local, equilateral and orthogonal (and in the context of limiting triangular configurations; enfolded) non-Gaussian features. Precisely these features have been chosen, as it has been shown theoretically that most models of inflation produce non-Gaussianities that fall in one of these three classes (for recent reviews see [14][15][16]).…”

Section: Introductionmentioning

confidence: 99%

Oscillations in the primordial bispectrum: Mode expansion

Meerburg¹

2010

Phys. Rev. D

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We consider the presence of oscillations in the primordial bispectrum, inspired by three different cosmological models; features in the primordial potential, resonant type non-Gaussianities and deviation from the standard Bunch Davies vacuum. In order to put constraints on their bispectra, a logical first step is to put these into factorized form which can be achieved via the recently proposed method of polynomial basis expansion on the tetrahedral domain. We investigate the viability of such an expansion for the oscillatory bispectra and find that one needs an increasing number of orthonormal mode functions to achieve significant correlation between the expansion and the original spectrum as a function of their frequency. To reduce the number of modes required, we propose a basis consisting of Fourier functions orthonormalized on the tetrahedral domain. We show that the use of Fourier mode functions instead of polynomial mode functions can lead to the necessary factorizability with the use of only 1/5 of the total number of modes required to reconstruct the bispectra with polynomial mode functions. Moreover, from an observational perspective, the expansion has unique signatures depending on the orientation of the oscillation due to a resonance effect between the mode functions and the original spectrum. This effect opens the possibility to extract information about both the frequency of the bispectrum as well as its shape while considering only a limited number of modes. The resonance effect is independent of the phase of the reconstructed bispectrum suggesting Fourier mode extraction could be an efficient way to detect oscillatory bispectra in the data.

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“…Having the numerical results about the momentum integrations (5.13)-(5.16), we can finally perform the x-integrations to obtain the reduced bispectra. In Figure (7) and ( 8), we plot the integrals l 2 (l 2 + 1)l 3 (l 3 + 1) x 2 dx b (α) to (η 0 − 0.1η * ), since the primary signals come from the recombination epoch η * . From Figure (7) and (8), we can see that in the Sachs-Wolfe (SW) regime (l ≤ 10) our result presents a SW plateau, which is consistent with that in [18].…”

Section: Numerical Resultsmentioning

confidence: 99%

Acoustic signatures in the Cosmic Microwave Background bispectrum from primordial magnetic fields

Cai

2010

J. Cosmol. Astropart. Phys.

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Using the full radiation transfer function, we numerically calculate the CMB angular bispectrum seeded by the compensated magnetic scalar density mode. We find that, for the string inspired primordial magnetic fields characterized by index n B = −2.9 and mean-field amplitude B λ = 9 nG, the angular bispectrum is dominated by two primordial magnetic shapes. The first magnetic shape looks similar to the one from local-type primordial curvature perturbations, so both the amplitude and profile of the Komatsu-Spergel estimator (reduced bispectrum) seeded by this shape are almost the same as those of the primary CMB anisotropies. However, for different parameter sets (l 1 , l 2 ), this "localtype" reduced bispectrum oscillates around different asymptotic values in the high-l 3 regime because of the effect of the Lorentz force, which is exerted by the primordial magnetic fields on the charged baryons. This feature is different from the standard case where all modes approach to zero asymptotically in the high-l limit. On the other hand, the second magnetic shape appears only in the primordial magnetic field model. The amplitude of the Komatsu-Spergel estimator sourced by the second shape diverges in the low-l regime because of the negative slope of shape. In the high-l regime, this amplitude is approximately equal to that of the first estimator, but with a reversal phase.

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Non-Gaussianity and the Cosmic Microwave Background Anisotropies

Cited by 30 publications

References 0 publications

Scale-dependent non-Gaussianity probes inflationary physics

Scale-dependent non-Gaussianity probes inflationary physics

Oscillations in the primordial bispectrum: Mode expansion

Acoustic signatures in the Cosmic Microwave Background bispectrum from primordial magnetic fields

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