Signatures of initial state modifications on bispectrum statistics

Meerburg, P. Daniel; Schaar, Jan Pieter van der; Corasaniti, Pier-Stefano

doi:10.1088/1475-7516/2009/05/018

Cited by 193 publications

(308 citation statements)

References 98 publications

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“…For instance, although DBI inflation does not produce a factorized bispectrum, it is well approximated by the equilateral template [18], that is factorized by construction. The same is true for both the local and orthogonal template, as well as the enfolded [24] template. However, the method for constructing such factorized approximations of existing theoretical bispectra is rather ad-hoc.…”

Section: Mode Expansion a Power Modesmentioning

confidence: 56%

“…In the following we will discuss the shapes of the bispectra and quote theoretically predicted ranges of their associated f N L . We would like to refer to the literature for a detailed examination of the theoretically predicted values of f N L [24,25,27,28] in various theoretical contexts.…”

Section: Oscillations In Primordial Bispectramentioning

confidence: 99%

“…Consequently, η 0 (k i ) will depend on the k i direction the BD vacuum has been perturbed in. This direction is set by the direction in which k i picks up a minus sign due to the Bunch Davies vacuum perturbation as explained in [24]. One could allow for scale invariance breaking and consider BEFT, however there are some suggestions [36] that such large scale invariance should have been observed already.…”

Section: Initial State Modificationsmentioning

confidence: 99%

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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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Section: Mode Expansion a Power Modesmentioning

confidence: 56%

Section: Oscillations In Primordial Bispectramentioning

confidence: 99%

Section: Initial State Modificationsmentioning

confidence: 99%

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Oscillations in the primordial bispectrum: Mode expansion

Meerburg¹

2010

Phys. Rev. D

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“…It is well known that if the initial vacuum state for inflation is excited and deviates from the standard Bunch-Davies vacuum, then measurable non-Gaussianities can be produced (Chen et al 2007b;Holman & Tolley 2008;Meerburg et al 2009;Ashoorioon & Shiu 2011). These models generically lead to non-Gaussianity that peaks in the flattened limit, where k 1 + k 2 ≈ k 3 , and also often has oscillatory behaviour.…”

Section: Non-gaussianity From Excited Initial Statesmentioning

confidence: 99%

Planck2015 results

Ade

Aghanim

Arnaud

et al. 2016

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The Planck full mission cosmic microwave background (CMB) temperature and E-mode polarization maps are analysed to obtain constraints on primordial non-Gaussianity (NG). Using three classes of optimal bispectrum estimators -separable template-fitting (KSW), binned, and modalwe obtain consistent values for the primordial local, equilateral, and orthogonal bispectrum amplitudes, quoting as our final result from temperature alone f local NL = 2.5 ± 5.7, f equil NL = −16 ± 70, and f ortho NL = −34 ± 33 (68% CL, statistical). Combining temperature and polarization data we obtain f local NL = 0.8 ± 5.0, f equil NL = −4 ± 43, and f ortho NL = −26 ± 21 (68% CL, statistical). The results are based on comprehensive cross-validation of these estimators on Gaussian and non-Gaussian simulations, are stable across component separation techniques, pass an extensive suite of tests, and are consistent with estimators based on measuring the Minkowski functionals of the CMB. The effect of time-domain de-glitching systematics on the bispectrum is negligible. In spite of these test outcomes we conservatively label the results including polarization data as preliminary, owing to a known mismatch of the noise model in simulations and the data. Beyond estimates of individual shape amplitudes, we present model-independent, three-dimensional reconstructions of the Planck CMB bispectrum and derive constraints on early universe scenarios that generate primordial NG, including general single-field models of inflation, axion inflation, initial state modifications, models producing parityviolating tensor bispectra, and directionally dependent vector models. We present a wide survey of scale-dependent feature and resonance models, accounting for the "look elsewhere" effect in estimating the statistical significance of features. We also look for isocurvature NG, and find no signal, but we obtain constraints that improve significantly with the inclusion of polarization. The primordial trispectrum amplitude in the local model is constrained to be g local NL = (−9.0 ± 7.7) × 10 4 (68% CL statistical), and we perform an analysis of trispectrum shapes beyond the local case. The global picture that emerges is one of consistency with the premises of the ΛCDM cosmology, namely that the structure we observe today was sourced by adiabatic, passive, Gaussian, and primordial seed perturbations.

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“…So far, the bispectrum shapes for which large-scalestructure predictions have been worked out include the local [14], equilateral [15], orthogonal [16], and folded [17] shapes, all of which are scale independent. However, there are several classes of inflationary models which predict bispectra that have strongly scale-dependent oscillatory features [17][18][19][20][21][22][23][24][25][26][27]. These models can circumvent the tight limit on the bispectrum in the squeezed configuration [28] by breaking the slow-roll approximation.…”

Section: Introductionmentioning

confidence: 99%

Oscillating bispectra and galaxy clustering: A novel probe of inflationary physics with large-scale structure

Cyr-Racine

2011

Phys. Rev. D

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Many models of inflation predict oscillatory features in the bispectrum of primordial fluctuations. Since it has been shown that primordial non-Gaussianity can lead to a scale-dependent halo bias, we investigate the effect of oscillations in the three-point function on the clustering of dark-matter halos. Interestingly, we find that features in the inflaton potential such as oscillations or sharp steps get imprinted in the mass dependence of the non-Gaussian halo bias. In this paper, we focus on models displaying a sharp feature in the inflaton potential as well as resonant non-Gaussianity. In both cases, we find a strong scale dependence for the non-Gaussian halo bias with a slope similar to that of the local model. In the resonant case, we find that the non-Gaussian bias oscillates with halo mass, a novel feature that is unique to this type of models. In the case of a sharp feature in the inflaton potential, we find that the clustering of halos is enhanced at the mass scale corresponding to the Fourier mode that exited the horizon when the inflaton was crossing the feature in the potential. Both of these are new effects that open the possibility of characterizing the inflationary potential with large-scale-structure surveys. We briefly discuss the prospects for detecting these non-Gaussian effects.

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Signatures of initial state modifications on bispectrum statistics

Cited by 193 publications

References 98 publications

Oscillations in the primordial bispectrum: Mode expansion

Oscillations in the primordial bispectrum: Mode expansion

Planck2015 results

Oscillating bispectra and galaxy clustering: A novel probe of inflationary physics with large-scale structure

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