Scale-invariant inflation

Rinaldi, Massimiliano; Cecchini, Chiara; Ghoshal, Anish; Mukherjee, Debangshu

doi:10.48550/arxiv.2303.16107

Cited by 1 publication

(3 citation statements)

References 21 publications

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“…2 The earlier works of refs. [189][190][191][192] have analytically confirmed that inflation in a scaleinvariant Universe as discussed in ref. [188] is a viable model for the origin of structure as far as inflationary observables are concerned.…”

Section: Jcap07(2024)058mentioning

confidence: 61%

“…In this picture inflation is then accompanied by a spontaneous/dynamical breaking of scale-invariance and the emergence of a mass scale not present in the original action. Subsequent works have established analytically that the spectral indices predicted by this model fall well within current experimental constraints [189][190][191], even when one-loop quantum corrections are considered [192]. Scale-invariance and inflation have also been studied in other papers.…”

Section: Jcap07(2024)058mentioning

confidence: 83%

“…In this work, we go significantly beyond earlier semi-analytical works, which studied the model's predictions for the inflationary parameters n s and r [189][190][191]. Our model predictions are derived by solving the full numerical dynamics of the system, making use of a method recently developed by some of us to study generic multi-field inflationary models JCAP07(2024)058 with potentially non-trivial field-space metric [231], and are confronted against the latest Planck and BICEP/Keck CMB observations to obtain the first robust constraints on the free parameters of the model.…”

Section: Discussionmentioning

confidence: 99%

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Testing scale-invariant inflation against cosmological data

Cecchini,

De Angelis,

Giarè

et al. 2024

J. Cosmol. Astropart. Phys.

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There is solid theoretical and observational motivation behind the idea of scale-invariance as a fundamental symmetry of Nature. We consider a recently proposed classically scale-invariant inflationary model, quadratic in curvature and featuring a scalar field non-minimally coupled to gravity. We go beyond earlier analytical studies, which showed that the model predicts inflationary observables in qualitative agreement with data, by solving the full two-field dynamics of the system — this allows us to corroborate previous analytical findings and set robust constraints on the model's parameters using the latest Cosmic Microwave Background (CMB) data from Planck and BICEP/Keck. We demonstrate that scale-invariance constrains the two-field trajectory such that the effective dynamics are that of a single field, resulting in vanishing entropy perturbations and protecting the model from destabilization effects. We derive tight upper limits on the non-minimal coupling strength, excluding conformal coupling at high significance. By explicitly sampling over them, we demonstrate an overall insensitivity to initial conditions. We argue that the model predicts a minimal level of primordial tensor modes set by r ≳ 0.003, well within the reach of next-generation CMB experiments. These will therefore provide a litmus test of scale-invariant inflation, and we comment on the possibility of distinguishing the model from Starobinsky and α-attractor inflation. Overall, we argue that scale-invariant inflation is in excellent health, and possesses features which make it an interesting benchmark for tests of inflation from future CMB data.

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