Primordial non-Gaussianities from multiple-field inflation

Seery, David; Lidsey, James E.

doi:10.1088/1475-7516/2005/09/011

Cited by 318 publications

(580 citation statements)

References 71 publications

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“…(6) will thus be 25/54 times the expression in the square brackets. (As a consistency check we note that in the limit r → 1 this result agrees with (27).) If there is non-linear evolution of the curvaton field, χ, between Hubble-exit and the start of the curvaton oscillation, such that gg ′′ /g ′ 2 ≃ −1, then from (41) we see that f NL can be small even when r → 0, see also [29,30].…”

Section: A First Ordersupporting

confidence: 66%

Non-Gaussianity of the primordial perturbation in the curvaton model

2006

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We use the δN -formalism to investigate the non-Gaussianity of the primordial curvature perturbation in the curvaton scenario for the origin of structure. We numerically calculate the full probability distribution function allowing for the non-instantaneous decay of the curvaton and compare this with analytic results derived in the sudden-decay approximation. We also present results for the leading-order contribution to the primordial bispectrum and trispectrum. In the suddendecay approximation we derive a fully non-linear expression relating the primordial perturbation to the initial curvaton perturbation. As an example of how non-Gaussianity provides additional constraints on model parameters, we show how the primordial bispectrum on CMB scales can be used to constrain variance on much smaller scales in the curvaton field. Our analytical and numerical results allow for multiple tests of primordial non-Gaussianity, and thus they can offer consistency tests of the curvaton scenario.

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Section: A First Ordersupporting

confidence: 66%

Non-Gaussianity of the primordial perturbation in the curvaton model

2006

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“…But allowing them to decay into both matter and radiation alone does not appear to stop them decaying quickly [34]. Even if ζ did evolve after reheating, our work is not redundant, however one would have to continue calculating the evolution until a later time 5 .…”

Section: Discussionmentioning

confidence: 99%

Influence of reheating on the trispectrum and its scale dependence

Leung¹,

Tarrant²,

Byrnes³

et al. 2013

J. Cosmol. Astropart. Phys.

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We study the evolution of the non-linear curvature perturbation during perturbative reheating, and hence how observables evolve to their final values which we may compare against observations. Our study includes the evolution of the two trispectrum parameters, gNL and τNL, as well as the scale dependence of both fNL and τNL. In general the evolution is significant and must be taken into account, which means that models of multifield inflation cannot be compared to observations without specifying how the subsequent reheating takes place. If the trispectrum is large at the end of inflation, it normally remains large at the end of reheating. In the classes of models we study, it remains very hard to generate τNL f 2 NL , regardless of the decay rates of the fields. Similarly, for the classes of models in which gNL τNL during slow-roll inflation, we find the relation typically remains valid during reheating. Therefore it is possible to observationally test such classes of models without specifying the parameters of reheating, even though the individual observables are sensitive to the details of reheating. It is hard to generate an observably large gNL however. The runnings, n f NL and nτ NL , tend to satisfy a consistency relation nτ NL = (3/2)n f NL regardless of the reheating timescale, but are in general too small to be observed for the class of models considered.

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“…This is generally the case [29], although there can be exceptions if the third derivative of the potential is large [30]. There is no analogous proof in the case of a non-trivial field metric, but since we are assuming the Riemann tensor is slow-roll suppressed this assumption is likely to remain valid, at least in the vast majority of cases.…”

Section: Evolution Of Field Fluctuationsmentioning

confidence: 96%

General formula for the running of local fNL

Byrnes¹,

Gong²

2013

Physics Letters B

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We compute the scale dependence of f NL for models of multi-field inflation, allowing for an arbitrary field space metric. We show that, in addition to multi-field effects and self interactions, the curved field space metric provides another source of scale dependence, which arises from the field-space Riemann curvature tensor and its derivatives. The scale dependence may be detectable within the near future if the amplitude of f NL is not too far from the current observational bounds.

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Primordial non-Gaussianities from multiple-field inflation

Cited by 318 publications

References 71 publications

Non-Gaussianity of the primordial perturbation in the curvaton model

Non-Gaussianity of the primordial perturbation in the curvaton model

Influence of reheating on the trispectrum and its scale dependence

General formula for the running of local fNL

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