A note on calm excited states of inflation

Ashoorioon, Amjad; Shiu, Gary

doi:10.1088/1475-7516/2011/03/025

Cited by 89 publications

(75 citation statements)

References 76 publications

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“…(45). The usual Fisher analysis leads to σ 2 fNL = (F −1 ) 00 , where the (1 + 4N bases ) × (1 + 4N bases ) Fisher matrix F nm is now defined from the total scalar product (57). We find that using seventh-order instead of thirdorder polynomials degrades the SNR by no more than ∼ 20 %.…”

Section: Tomographymentioning

confidence: 90%

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Primordial non-gaussianity from the bispectrum of 21-cm fluctuations in the dark ages

2015

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A measurement of primordial non-gaussianity will be of paramount importance to distinguish between different models of inflation. Cosmic microwave background (CMB) anisotropy observations have set unprecedented bounds on the non-gaussianity parameter fNL but the interesting regime fNL 1 is beyond their reach. Brightness-temperature fluctuations in the 21-cm line during the dark ages (z ∼ 30 − 100) are a promising successor to CMB studies, giving access to a much larger number of modes. They are, however, intrinsically non-linear, which results in secondary non-gaussianities orders of magnitude larger than the sought-after primordial signal. In this paper we carefully compute the primary and secondary bispectra of 21-cm fluctuations on small scales. We use the flat-sky formalism, which greatly simplifies the analysis, while still being very accurate on small angular scales. We show that the secondary bispectrum is highly degenerate with the primordial one, and argue that even percent-level uncertainties in the amplitude of the former lead to a bias of order ∆fNL ∼ 10. To tackle this problem we carry out a detailed Fisher analysis, marginalizing over the amplitudes of a few smooth redshift-dependent coefficients characterizing the secondary bispectrum. We find that the signal-to-noise ratio for a single redshift slice is reduced by a factor of ∼ 5 in comparison to a case without secondary non-gaussianities. Setting aside foreground contamination, we forecast that a cosmic-variance-limited experiment observing 21-cm fluctuations over 30 ≤ z ≤ 100 with a 0.1-MHz bandwidth and 0.1-arcminute angular resolution could achieve a sensitivity of order f local NL ∼ 0.03, f equil NL ∼ 0.04 and f ortho NL ∼ 0.03.

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Section: Tomographymentioning

confidence: 90%

“…Initial conditions different from the standard Bunch-Davies vacuum would give rise to this kind of PNG [57]. It can be expressed as a combination of the two above, as B folded = B equil − B ortho /2.…”

Section: Orthogonalmentioning

confidence: 99%

Primordial non-gaussianity from the bispectrum of 21-cm fluctuations in the dark ages

2015

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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

A&A

477

256

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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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“…Secondly, the generation of initial perturbations is a stochastic process, and quantities like the primordial curvature perturbation or the matter density fluctualxiv We should also highlight several works that further consider features and enhancements to the three point function of the adiabatic mode from modified initial states [308][309][310][311] that in certain contexts, can also be arranged to preserve the scale invariance of the two point function [312,313].…”

Section: Observables: Measuring Spatial Fluctuationsmentioning

confidence: 99%

Features and new physical scales in primordial observables: Theory and observation

Chluba

Hamann

Patil

2015

Int. J. Mod. Phys. D

212

233

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June 22, 20152 All cosmological observations to date are consistent with adiabatic, Gaussian and nearly scale invariant initial conditions. These findings provide strong evidence for a particular symmetry breaking pattern in the very early universe (with a close to vanishing order parameter, ), widely accepted as conforming to the predictions of the simplest realizations of the inflationary paradigm. However, given that our observations are only privy to perturbations, in inferring something about the background that gave rise to them, it should be clear that many different underlying constructions project onto the same set of cosmological observables. Features in the primordial correlation functions, if present, would offer a unique and discriminating window onto the parent theory in which the mechanism that generated the initial conditions is embedded. In certain contexts, simple linear response theory allows us to infer new characteristic scales from the presence of features that can break the aforementioned degeneracies among different background models, and in some cases can even offer a limited spectroscopy of the heavier degrees of freedom that couple to the inflaton. In this review, we offer a pedagogical survey of the diverse, theoretically well grounded mechanisms which can imprint features into primordial correlation functions in addition to reviewing the techniques one can employ to probe observations. These observations include cosmic microwave background anisotropies and spectral distortions as well as the matter two and three point functions as inferred from large-scale structure and potentially, 21 cm surveys.

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A note on calm excited states of inflation

Cited by 89 publications

References 76 publications

Primordial non-gaussianity from the bispectrum of 21-cm fluctuations in the dark ages

Primordial non-gaussianity from the bispectrum of 21-cm fluctuations in the dark ages

Planck2015 results

Features and new physical scales in primordial observables: Theory and observation

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