Starobinsky cosmological model in Palatini formalism

Stachowski, Aleksander; Szydłowski, Marek; Borowiec, A.

doi:10.1140/epjc/s10052-017-4981-8

Cited by 57 publications

(48 citation statements)

References 118 publications

(138 reference statements)

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“…so that the Einstein frame potential for the canonically normalized field becomes 20) where the expressions in the metric case apply for ξ 1 and χ 3/2M P , and the expressions in the Palatini case are exact. We see that for χ 3/2M P in the metric case or χ M P / √ ξ in the Palatini case the potential tends to a constant exponentially fast and is therefore suitable for slow-roll inflation.…”

Section: Higgs Inflationmentioning

confidence: 99%

Tracing the high energy theory of gravity: an introduction to Palatini inflation

Tenkanen

2020

Gen Relativ Gravit

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We present an introduction to cosmic inflation in the context of Palatini gravity, which is an interesting alternative to the usual metric theory of gravity. In the latter case only the metric g µν determines the geometry of space-time, whereas in the former case both the metric and the space-time connection Γ λ µν are a priori independent variables -a choice which can lead to a theory of gravity different from the metric one. In scenarios where the field(s) responsible for cosmic inflation are coupled non-minimally to gravity or the gravitational sector is otherwise extended, assumptions of the underlying gravitational degrees of freedom can have a big impact on the observational consequences of inflation. We demonstrate this explicitly by reviewing several interesting and well-motivated scenarios including Higgs inflation, R 2 inflation, and ξ-attractor models. We also discuss some prospects for future research and argue why r = 10 −3 is a particularly important goal for future missions that search for signatures of primordial gravitational waves.

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Section: Higgs Inflationmentioning

confidence: 99%

Tracing the high energy theory of gravity: an introduction to Palatini inflation

Tenkanen

2020

Gen Relativ Gravit

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“…For this case we prefer to use m 2 , instead of λ, since it carries dimension of mass 2 when m P is reinstated. This models has been discussed in [32] and belongs to the class of the cosmological attractors [74], which is clearly seen if one uses the canonically normalized field φ, see (19). However no need to do that as we prefer to work directly with the non canonical field h instead.…”

Section: Model Imentioning

confidence: 99%

Reheating in R2 Palatini inflationary models

Gialamas

Lahanas

2020

Phys. Rev. D

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We consider R 2 inflation in the Palatini gravity assuming the existence of scalar fields, coupled to gravity in the most general manner. These theories, in the Einstein frame, and for one scalar field h, share common features with K -inflation models. We apply this formalism for the study of popular inflationary models, whose potentials are monomials, V ∼ h n , with n a positive even integer. We also study the Higgs model non-minimally coupled to gravity. Although these have been recently studied, in the framework of the Palatini approach, we show that the scalar power spectrum severely constrains these models. Although we do not propose a particular reheating mechanism, we show that the quadratic ∼ h 2 and the Higgs model can survive these constraints with a maximum reheating temperature as large as ∼ 10 15 GeV , when reheating is instantaneous. However, this can be only attained at the cost of a delicate fine-tuning of couplings. Deviations from this fine-tuned values can still yield predictions compatible with the cosmological data, for couplings that lie in very tight range, giving lower reheating temperatures.

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“…To handle the field equations (2) in a more convenient way for the sake of the problem considered here, we use the fact that they can be rewritten in the terms of the conformal metric h µν [40,41] and the scalar field Φ ≡ f R asR…”

Section: Stellar Equilibrium Equations In Palatini F (R) Gravitymentioning

confidence: 99%

Minimum main sequence mass in quadratic Palatini f(R) gravity

2019

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General Relativity yields an analytical prediction of a minimum required mass of roughly ∼ 0.08 − 0.09M for a star to stably burn sufficient hydrogen to fully compensate photospheric losses and, therefore, to belong to the main sequence. Those objects below this threshold (brown dwarfs) eventually cool down without any chance to stabilize their internal temperature. In this work we consider quadratic Palatini f (R) gravity and show that the corresponding newtonian hydrostatic equilibrium equation contains a new term whose effect is to introduce a weakening/strenghtening of the gravitational interaction inside astrophysical bodies. This fact modifies the General Relativity prediction for this minimum main sequence mass. Through a crude analytical modelling we use this result in order to constraint a combination of the quadratic f (R) gravity parameter and the central density according to astrophysical observations.

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Starobinsky cosmological model in Palatini formalism

Cited by 57 publications

References 118 publications

Tracing the high energy theory of gravity: an introduction to Palatini inflation

Tracing the high energy theory of gravity: an introduction to Palatini inflation

Reheating in R2 Palatini inflationary models

Minimum main sequence mass in quadratic Palatini f(R) gravity

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