Non-Gaussian CMB and LSS statistics beyond polyspectra

Palma, Gonzalo A.; Scheihing-Hitschfeld, Bruno; Sypsas, Spyros

doi:10.1088/1475-7516/2020/02/027

Cited by 12 publications

(9 citation statements)

References 183 publications

(336 reference statements)

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“…In such models, not only ζ 3 c and ζ 4 c , but all n-point moments are expected to contribute corrections of order 1 on the tail of the distribution, making the expansion (1.2) useless to study extreme fluctuations. This failure of perturbation theory to parametrise large statistical excursions of ζ in certain models of inflation motivates the consideration of non-perturbative techniques to study the consequence of non-linear interactions of ζ during inflation [13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

The hand-made tail: non-perturbative tails from multifield inflation

Achúcarro

Céspedes

Davis

et al. 2022

J. High Energ. Phys.

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It is becoming increasingly clear that large but rare fluctuations of the primordial curvature field, controlled by the tail of its probability distribution, could have dramatic effects on the current structure of the universe — e.g. via primordial black-holes. However, the use of standard perturbation theory to study the evolution of fluctuations during inflation fails in providing a reliable description of how non-linear interactions induce non-Gaussian tails. Here, we use the stochastic inflation formalism to study the non-perturbative effects from multi-field fluctuations on the statistical properties of the primordial curvature field. Starting from the effective action describing multi-field fluctuations, we compute the joint probability density function and show that enhanced non-Gaussian tails are a generic feature of slow-roll inflation with additional degrees of freedom.

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Section: Introductionmentioning

confidence: 99%

The hand-made tail: non-perturbative tails from multifield inflation

Achúcarro

Céspedes

Davis

et al. 2022

J. High Energ. Phys.

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“…Another effect is the generation of non-Gaussianity, along the lines of Refs. [59,75,76]. A large λ will induce non-Gaussian deformations to the statistics of ζ that could change the details of PBH formation [77][78][79][80][81][82][83][84][85][86].…”

mentioning

confidence: 99%

Seeding Primordial Black Holes in Multifield Inflation

2020

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The inflationary origin of primordial black holes (PBHs) relies on a large enhancement of the power spectrum Δ ζ of the curvature fluctuation ζ at wavelengths much shorter than those of the cosmic microwave background anisotropies. This is typically achieved in models where ζ evolves without interacting significantly with additional (isocurvature) scalar degrees of freedom. However, quantum gravity inspired models are characterized by moduli spaces with highly curved geometries and a large number of scalar fields that could vigorously interact with ζ (as in the cosmological collider picture). Here we show that isocurvature fluctuations can mix with ζ inducing large enhancements of its amplitude. This occurs whenever the inflationary trajectory experiences rapid turns in the field space of the model leading to amplifications that are exponentially sensitive to the total angle swept by the turn, which induce characteristic observable signatures on Δ ζ. We derive accurate analytical predictions and show that the large enhancements required for PBHs demand noncanonical kinetic terms in the action of the multifield system.

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“…However, since we are considering an effective excited state emerging at some later time, the "quantum" character here translates into a statistical property of the random variable h: all the terms in the expansion (3.10) express the non-Gaussian variable 10 as a series over the Gaussian random fields h 0 , Q 0 much like the familiar local ansatz [71] for the scalar fluctuation (see also App. A.1 of [72] for a related discussion).…”

Section: Multifield Quantisationmentioning

confidence: 99%

Primordial gravitational waves from excited states

Fumagalli,

Palma,

Renaux-Petel

et al. 2021

Preprint

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We show that a scalar excited state with large occupation numbers during inflation leads to an enhancement of tensor modes and a characteristic pattern of orderone oscillations in the associated stochastic gravitational wave background (SGWB) sourced during inflation. An effective excited state, i.e. a departure from the Bunch-Davies vacuum, can emerge dynamically as the result of a transient non-adiabatic evolution, e.g. a sharp feature along the inflationary history. We provide an explicit example in a multifield context where the sharp feature triggering the excited state is identified with a strong turn in the inflationary trajectory. En passant, we derive a universal expression for the tensor power spectrum sourced at second order by an arbitrary number of scalar degrees of freedom during inflation, crucially taking into account the nontrivial structure of the Hilbert space in multifield setups. The SGWB sourced during inflation can overcome the standard scalar-induced SGWB sourced at horizon re-entry of the fluctuations after inflation, while being less constrained by perturbativity and backreaction bounds. In addition, one may entertain the possibility of detecting both since they peak at different frequencies exhibiting oscillations with distinct periods.

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Non-Gaussian CMB and LSS statistics beyond polyspectra

Cited by 12 publications

References 183 publications

The hand-made tail: non-perturbative tails from multifield inflation

The hand-made tail: non-perturbative tails from multifield inflation

Seeding Primordial Black Holes in Multifield Inflation

Primordial gravitational waves from excited states

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