Simplifying the EFT of Inflation: generalized disformal transformations and redundant couplings

Bordin, Lorenzo; Cabass, Giovanni; Creminelli, Paolo; Vernizzi, Filippo

doi:10.1088/1475-7516/2017/09/043

Cited by 34 publications

(47 citation statements)

References 20 publications

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“…This is true even though we allow for boost breaking interactions. This is a particular case of a more general set of results obtained in [59][60][61], where it was also concluded that the first boost breaking ψ φφγ generated from coupling to the inflaton foliation of time comes at three-derivatives. In that work the authors work at the level of the Lagrangian and use field redefinitions to remove redundant couplings in the EFT of inflation.…”

Section: A Massless Scalar Coupled To Gravitymentioning

confidence: 73%

“…• It would be interesting to investigate the extent to which our bootstrap approach can remove redundancies in the EFT of inflation. This has been considered in [59][60][61] at the level of the Lagrangian where field redefinitions were used to remove redundant interactions. Our on-shell approach should make this process particularly simple and transparent.…”

Section: Summary and Future Directionsmentioning

confidence: 99%

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From locality and unitarity to cosmological correlators

Jazayeri

Pajer

Stefanyszyn

2021

J. High Energ. Phys.

118

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In the standard approach to deriving inflationary predictions, we evolve a vacuum state in time according to the rules of a given model. Since the only observables are the future values of correlators and not their time evolution, this brings about a large degeneracy: a vast number of different models are mapped to the same minute number of observables. Furthermore, due to the lack of time-translation invariance, even tree-level calculations require an increasing number of nested integrals that quickly become intractable. Here we ask how much of the final observables can be “bootstrapped” directly from locality, unitarity and symmetries.To this end, we introduce two new “boostless” bootstrap tools to efficiently compute tree-level cosmological correlators/wavefunctions without any assumption about de Sitter boosts. The first is a Manifestly Local Test (MLT) that any n-point (wave)function of massless scalars or gravitons must satisfy if it is to arise from a manifestly local theory. When combined with a sub-set of the recently proposed Bootstrap Rules, this allows us to compute explicitly all bispectra to all orders in derivatives for a single scalar. Since we don’t invoke soft theorems, this can also be extended to multi-field inflation. The second is a partial energy recursion relation that allows us to compute exchange correlators. Combining a bespoke complex shift of the partial energies with Cauchy’s integral theorem and the Cosmological Optical Theorem, we fix exchange correlators up to a boundary term. The latter can be determined up to contact interactions using unitarity and manifest locality. As an illustration, we use these tools to bootstrap scalar inflationary trispectra due to graviton exchange and inflaton self-interactions.

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Section: A Massless Scalar Coupled To Gravitymentioning

confidence: 73%

Section: Summary and Future Directionsmentioning

confidence: 99%

From locality and unitarity to cosmological correlators

Jazayeri

Pajer

Stefanyszyn

2021

J. High Energ. Phys.

118

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“…There comes an important advantage of the unitary gauge: it allows to write down the most general action for linear cosmological perturbations with relative ease, providing an effective framework that does not rely on any specific model, yet being a genuine description of departures from GR: a so-called effective field theory (EFT). Regarding expanding universe, this formalism was first applied to inflation [37,38,39], then to quintessence models without conformal couplings [40], and finally to DE [41,42]. The latter case enables one to treat any DE/MG models with one additional scalar DoF in a model-independent approach described through a variety of geometrical operators compatible with the symmetry imposed and accompanied by time dependent functions, namely the EFT functions.…”

Section: Introductionmentioning

confidence: 99%

Effective field theory of dark energy: A review

2020

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The discovery of cosmic acceleration has triggered a consistent body of theoretical work aimed at modeling its phenomenology and understanding its fundamental physical nature. In recent years, a powerful formalism that accomplishes both these goals has been developed, the so-called effective field theory of dark energy. It can capture the behavior of a wide class of modified gravity theories and classify them according to the imprints they leave on the smooth background expansion history of the Universe and on the evolution of linear perturbations. The effective field theory of dark energy is based on a Lagrangian description of cosmological perturbations which depends on a number of functions of time, some of which are non-minimal couplings representing genuine deviations from standard gravity. Such a formalism is thus particularly convenient to fit and interpret the wealth of new data that will be provided by future galaxy surveys. Despite its recent appearance, this formalism has already allowed a systematic investigation of what lies beyond the standard gravity landscape and provided a conspicuous amount of theoretical predictions and observational results. In this review, we report on these achievements. Conclusion and outlook 94Appendix A Acronyms and symbols 971. Scalar-tensor theoriesà la Brans-Dicke, hereafter dubbed Generalized

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“…For more general inflationary frameworks, see also, e.g.,[40][41][42][43][44][45][46][47][48]. For a review on inflationary gravitational waves containting other examples, see[49].…”

mentioning

confidence: 99%

Parity breaking signatures from a Chern-Simons coupling during inflation: the case of non-Gaussian gravitational waves

Bartolo

Orlando

2017

J. Cosmol. Astropart. Phys.

108

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Considering high-energy modifications of Einstein gravity during inflation is an interesting issue. We can constrain the strength of the new gravitational terms through observations of inflationary imprints in the actual universe. In this paper we analyze the effects on slow-roll models due to a Chern-Simons term coupled to the inflaton field through a generic coupling function f (φ). A well known result is the polarization of primordial gravitational waves (PGW) into left and right eigenstates, as a consequence of parity breaking. In such a scenario the modifications to the power spectrum of PGW are suppressed under the conditions that allow to avoid the production of ghost gravitons at a certain energy scale, the so-called Chern-Simons mass M CS . In general it has been recently pointed out that there is very little hope to efficiently constrain chirality of PGW on the basis solely of two-point statistics from future CMB data, even in the most optimistic cases. Thus we search if significant parity breaking signatures can arise at least in the bispectrum statistics. We find that the tensor-tensor-scalar bispectra γγζ for each polarization state are the only ones that are not suppressed. Their amplitude, setting the level of parity breaking during inflation, is proportional to the second derivative of the coupling function f (φ) and they turn out to be maximum in the squeezed limit. We comment on the squeezed-limit consistency relation arising in the case of chiral gravitational waves, and on possible observables to constrain these signatures.

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Simplifying the EFT of Inflation: generalized disformal transformations and redundant couplings

Cited by 34 publications

References 20 publications

From locality and unitarity to cosmological correlators

From locality and unitarity to cosmological correlators

Effective field theory of dark energy: A review

Parity breaking signatures from a Chern-Simons coupling during inflation: the case of non-Gaussian gravitational waves

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