Non-Standard Hierarchies of the Runnings of the Spectral Index in Inﬂation

Longden, Chris

doi:10.3390/universe3010017

Cited by 4 publications

(3 citation statements)

References 42 publications

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“…To be concrete, in section 5 we investigate some kinetic couplings making comparisons among them. In particular, in subsection 5.1 we deepen and complete the study of [25,29] by showing that even though the correlation between the two perturbations is strong, an enlargement of the scalar spectral runnings is not present. Our conclusions can be found in section 6.…”

Section: Introductionmentioning

confidence: 94%

Adiabatic and isocurvature perturbations in extended theories with kinetic couplings

De Angelis,

van de Bruck

2023

J. Cosmol. Astropart. Phys.

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The scalar field sector in low-energy effective field theories motivated by string theory often contains several scalar fields, some of which possess non-standard kinetic terms. In this paper we study theories with two scalar fields, in which one of the fields has a non-canonical kinetic term. The kinetic coupling is allowed to depend on both fields, going beyond the work in the literature, which usually considers the case of the coupling to depend on the other field only. Our aim is to study adiabatic and isocurvature perturbations in these extended theories. Our results show that the evolution equation for the curvature perturbation does not change when allowing the coupling to depend on both fields, while the effective mass of the entropy perturbation changes. We find expressions for the spectral index and its running at horizon crossing and at the end of inflation. We apply the formalism and study three phenomenological models, with different kinetic couplings.

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Section: Introductionmentioning

confidence: 94%

Adiabatic and isocurvature perturbations in extended theories with kinetic couplings

De Angelis,

van de Bruck

2023

J. Cosmol. Astropart. Phys.

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“…For single field inflationary models, the above runnings are of the order of α s ∼ 10 −3 and β s ∼ 10 −5 [37,38]. Discriminating among α s and β s of different models is still an experimental challenge, however it might be possible to use α s to this purpose in forthcoming Stage-4 CMB experiments, see e.g.…”

Section: A Power Law Extension Of the Starobinsky Modelmentioning

confidence: 99%

Reconstructing af(R) theory from the α-Attractors

Miranda

Fabris

Piattella

2017

J. Cosmol. Astropart. Phys.

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Abstract. We show an analogy at high curvature between a f (R) = R + aR n−1 + bR 2 theory and the α-Attractors. We calculate the expressions of the parameters a, b and n as functions of α and the predictions of the model f (R) = R+aR n−1 +bR 2 on the scalar spectral index n s and the tensor-to-scalar ratio r. We find that the power law correction R n−1 allows for a production of gravitational waves enhanced with respect to the one in the Starobinsky model, while maintaining a viable prediction on n s . We numerically reconstruct the full α-Attractors class of models testing the goodness of our high-energy approximation f (R) = R + aR n−1 + bR 2 . Moreover, we also investigate the case of a single power law f (R) = γR 2−δ theory, with γ and δ free parameters. We calculate analytically the predictions of this model on the scalar spectral index n s and the tensor-to-scalar ratio r and the values of δ which are allowed from the current observational results. We find that −0.015 < δ < 0.016, confirming once again the excellent agreement between the Starobinsky model and observation.

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“…Tere are appealing related discussions with regard to the application and implementation of these ideas [36][37][38][39][40][41][42].…”

Section: Introductionmentioning

confidence: 99%

A Study of the Early Cosmic Dynamics in a Multifield Model of Inflation and Curvature Perturbations

Mughal,

Khan,

Awwad

et al. 2024

Advances in Astronomy

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In this work, we study the cosmological dynamics of the early universe by employing a small field potential in the context of multifield inflation. By investigating analytically the cosmological observables, such as the number of e-folds N, potential slow-roll parameters ϵV, ηV, and spectral index ns which carry significant information, we show that they impact the inflationary universe considerably. The tensor-to-scalar ratio concerning the curvature perturbation is worked out for the potential under consideration which is another significant observable and comes out to be nonnegative. In multifield models of inflation, both types of curvature and isocurvature perturbations exist, while, in the present work, during the slow-roll, isocurvature perturbations are suppressed and therefore can be neglected. The surviving perturbations which are due to the curvature only can be tackled suitably by a mechanism developed by Sasaki and Stewart known as Sasaki–Stewart formalism. The effect of augmenting the number of e-folds on the power spectrum through the spectral index and its impact on the observable parameters of the slow-roll inflationary phase is observed by carrying out the analysis. It is observed analytically that the spectrum of multifield inflation is effectively different than its corresponding single-field inflation. The field values and their masses affect the results profoundly at the time of horizon-crossing.

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Non-Standard Hierarchies of the Runnings of the Spectral Index in Inﬂation

Cited by 4 publications

References 42 publications

Adiabatic and isocurvature perturbations in extended theories with kinetic couplings

Adiabatic and isocurvature perturbations in extended theories with kinetic couplings

Reconstructing af(R) theory from the α-Attractors

A Study of the Early Cosmic Dynamics in a Multifield Model of Inflation and Curvature Perturbations

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