Scalar perturbations during multiple-field slow-roll inflation

Nibbelink, Stefan Groot; Tent, B. J. W. van

doi:10.1088/0264-9381/19/4/302

Cited by 248 publications

(371 citation statements)

References 61 publications

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“…These are formally the same equations as those of linear perturbation theory for the Sasaki-Mukhanov variables with the k 2 terms dropped [12]. Note that although equation (23) …”

Section: Long Wavelength Dynamicsmentioning

confidence: 94%

Non-linear inflationary perturbations

Rigopoulos

Shellard

2005

J. Cosmol. Astropart. Phys.

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We present a method by which cosmological perturbations can be quantitatively studied in single and multi-field inflationary models beyond linear perturbation theory. A non-linear generalization of the gauge-invariant Sasaki-Mukhanov variables is used in a long-wavelength approximation. These generalized variables remain invariant under time slicing changes on long wavelengths. The equations they obey are relatively simple and can be formulated for a number of time slicing choices. Initial conditions are set after horizon crossing and the subsequent evolution is fully non-linear. We briefly discuss how these methods can be implemented numerically to the study of non-Gaussian signatures from specific inflationary models.

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“…These are formally the same equations as those of linear perturbation theory for the Sasaki-Mukhanov variables with the k 2 terms dropped [12]. Note that although equation (23) …”

Section: Long Wavelength Dynamicsmentioning

confidence: 94%

Non-linear inflationary perturbations

Rigopoulos

Shellard

2005

J. Cosmol. Astropart. Phys.

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“…For inflaton trajectories in a curved field space, the covariant formalism of multi-field inflation [60,[62][63][64][65] provides a powerful tool to describe the background dynamics and perturbations. Consider a turning trajectory with ρ = ρ 0 , then the field velocity of the canonically normalized inflation is given byφ 2 = G abφ aφb = f (ρ)θ 2 , where the dot denotes the derivative with respect to the cosmic time.…”

Section: The Multi-field Analysis Of the Massive Fieldmentioning

confidence: 99%

On the inflationary massive field with a curved field manifold

Wang

2020

J. Cosmol. Astropart. Phys.

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Massive fields during inflation provide an interesting opportunity to test new physics at very high energy scales. Meanwhile in fundamental realizations, the inflationary field space typically has a curved geometry, which may leave detectable imprints in primordial observables. In this paper we study an extension of quasi-single field inflation where the inflaton and the massive field belong to a curved field manifold. Because of the nontrivial field space curvature, the massive field here can get significant mass corrections of order the Hubble scale, thus the quasi-single field predictions on primordial non-Gaussianity are affected. We derive the same result in an equivalent approach by using the background effective field theory of inflation, where a dimension-6 operator is identified to play an important role and its cutoff scale is associated with the curvature scale of the field space. In addition, due to the slow-roll evolution of the inflaton, this type of mass correction has intrinsic time-dependence. Consequently, the running mass modifies the scaling behaviour in the squeezed limit of the scalar bispectrum, while the resulting running index measures the curvature of the internal field space. Therefore the minimal setup of a massive field within curved field space during inflation may naturally lead to new observational signatures of the field space geometry.

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“…Thus, 8 An alternative notation to describe turns consists of defining the dimensionless parameter η ⊥ =θ/H, which was originally introduced in ref. [46,47], and its notation stems from the definition of a vector η a ≡ −φ a 0 /(Hφ0) [48] in order to extend the definition of the usual η parameter to the multi-field case. In this setting, η ⊥ is simply the projection of η a along the normal direction N a .…”

Section: Parametrizing Perturbationsmentioning

confidence: 99%

Effective theories of single field inflation when heavy fields matter

Achúcarro

Gong

Hardeman

et al. 2012

J. High Energ. Phys.

185

284

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We compute the low energy effective field theory (EFT) expansion for singlefield inflationary models that descend from a parent theory containing multiple other scalar fields. By assuming that all other degrees of freedom in the parent theory are sufficiently massive relative to the inflaton, it is possible to derive an EFT valid to arbitrary order in perturbations, provided certain generalized adiabaticity conditions are respected. These conditions permit a consistent low energy EFT description even when the inflaton deviates off its adiabatic minimum along its slowly rolling trajectory. By generalizing the formalism that identifies the adiabatic mode with the Goldstone boson of this spontaneously broken time translational symmetry prior to the integration of the heavy fields, we show that this invariance of the parent theory dictates the entire non-perturbative structure of the descendent EFT. The couplings of this theory can be written entirely in terms of the reduced speed of sound of adiabatic perturbations. The resulting operator expansion is distinguishable from that of other scenarios, such as standard single inflation or DBI inflation. In particular, we re-derive how certain operators can become transiently strongly coupled along the inflaton trajectory, consistent with slow-roll and the validity of the EFT expansion, imprinting features in the primordial power spectrum, and we deduce the relevant cubic operators that imply distinct signatures in the primordial bispectrum which may soon be constrained by observations.

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Scalar perturbations during multiple-field slow-roll inflation

Cited by 248 publications

References 61 publications

Non-linear inflationary perturbations

Non-linear inflationary perturbations

On the inflationary massive field with a curved field manifold

Effective theories of single field inflation when heavy fields matter

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