Deforming the Starobinsky model in ghost-free higher derivative supergravities

Diamandis, G.A.; Georgalas, B.C.; Kaskavelis, K.; Lahanas, A.B.; Pavlopoulos, Georgios A.

doi:10.1103/physrevd.96.044033

Cited by 10 publications

(7 citation statements)

References 100 publications

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“…The model under consideration is analysed in its basic characteristics in [20]. It is a higher R supergravity model described by the following functions of chiral superfields,…”

Section: Setting the Modelmentioning

confidence: 99%

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Multi-field inflation from a higher derivative N = 1 Supergravity model

Diamandis,

Georgalas,

Kaskavelis

et al. 2020

Preprint

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We study the cosmological evolution of a N = 1 supergravity model, dual to a higher derivative supergravity model coupled to scalar fields so that in the Einstein frame the model is ghost free. We find that this model admit slow roll inflationary solutions showing essentially two-field inflation. The cosmological parameters calculated for this model lie in acceptable range with corrections of the order lnN/N , N being the number of e-foldings, compared to the Starobinsky inflation model.

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“…The model under consideration is analysed in its basic characteristics in [20]. It is a higher R supergravity model described by the following functions of chiral superfields,…”

Section: Setting the Modelmentioning

confidence: 99%

“…From now on we take f 0 = 1/2 which is necessary in order to have canonically normalized Einstein gravity in the dual description, see[20] 4 An inflation scenario of hill-top form is not considered in this work.…”

mentioning

confidence: 99%

Multi-field inflation from a higher derivative N = 1 Supergravity model

Diamandis,

Georgalas,

Kaskavelis

et al. 2020

Preprint

Self Cite

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“…While the latter can exhibit (super-)renormalizability and locality, they are usually plagued with ghosts; the former, on their turn, may be ghost-free but present non-locality [54]. Applications of both approaches to inflationary context are found in the literature [59][60][61][62][63][64][65][66][67][68][69]. In particular, theories with an infinite number of derivatives are able to modify the tensor-to-scalar ratio [66][67][68].…”

Section: Introductionmentioning

confidence: 99%

Higher-order modified Starobinsky inflation

Cuzinatto

Medeiros

Pompeia

2019

J. Cosmol. Astropart. Phys.

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An extension of the Starobinsky model is proposed. Besides the usual Starobinsky Lagrangian, a term proportional to the derivative of the scalar curvature, ∇µR∇ µ R, is considered. The analyzis is done in the Einstein frame with the introduction of a scalar field and a vector field. We show that inflation is attainable in our model, allowing for a graceful exit. We also build the cosmological perturbations and obtain the leading-order curvature power spectrum, scalar and tensor tilts and tensor-to-scalar ratio. The tensor and curvature power spectrums are compared to the most recent observations from BICEP2/Keck collaboration. We verify that the scalar-to-tensor rate r can be expected to be up to three times the values predicted by Starobinsky model.Hence, the fluid represented by Eq. (9) has no contribution from viscous shear components, which are null here. Notice that the heat flux vector exists solely due to the higher order term -were it absent, the theory would be reduced to Starobinsky's model and, therefore, would be represented by a perfect fluid energy-momentum tensor. The above equations are specified in FLRW spacetime in the next section.

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“…String-inspired theories [42][43][44] and gauge-invariant gravity theories [45] suggest that a possible suitable modification is to consider higher-order derivatives of the curvature-related objects (R, R µν , R µ νρσ ); these theories will henceforth be called higher-order theories of gravity. This possibility of extension to GR has drawn the attention of the community as a possibility to address inflation [46][47][48][49][50][51][52][53][54], efforts toward a meaningful quantization of gravity [55][56][57][58] or the issue of ghost plagued models [59][60][61][62] -see also [63].…”

Section: Introductionmentioning

confidence: 99%

f(R,∇μ1R,…,∇
Cuzinatto
¹
,
Melo
²
,
Medeiros
³

et al. 2019
Phys. Rev. D
16
0
4
0
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In Cuzinatto et al. [Phys. Rev. D 93, 124034 (2016)], it has been demonstrated that theories of gravity in which the Lagrangian includes terms depending on the scalar curvature R and its derivatives up to order n , i.e. f (R, ∇µR, ∇µ 1 ∇µ 2 R, . . . , ∇µ 1 . . . ∇µ n R) theories of gravity, are equivalent to scalar-multitensorial theories in the Jordan frame. In particular, in the metric and Palatini formalisms, this scalar-multitensorial equivalent scenario shows a structure that resembles that of the Brans-Dicke theories with a kinetic term for the scalar field with ω0 = 0 or ω0 = −3/2, respectively. In the present work, the aforementioned analysis is extended to the Einstein frame. The conformal transformation of the metric characterizing the transformation from Jordan's to Einstein's frame is responsible for decoupling the scalar field from the scalar curvature and also for introducing a usual kinetic term for the scalar field in the metric formalism. In the Palatini approach, this kinetic term is absent in the action. Concerning the other tensorial auxiliary fields, they appear in the theory through a generalized potential. As an example, the analysis of an extension of the Starobinsky model (with an extra term proportional to ∇µR∇ µ R) is performed and the fluid representation for the energy-momentum tensor is considered. In the metric formalism, the presence of the extra term causes the fluid to be an imperfect fluid with a heat flux contribution; on the other hand, in the Palatini formalism the effective energy-momentum tensor for the extended Starobinsky gravity is that of a perfect fluid type. Finally, it is also shown that the extra term in the Palatini formalism represents a dynamical field which is able to generate an inflationary regime without a graceful exit.

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Deforming the Starobinsky model in ghost-free higher derivative supergravities

Cited by 10 publications

References 100 publications

Multi-field inflation from a higher derivative N = 1 Supergravity model

Multi-field inflation from a higher derivative N = 1 Supergravity model

Higher-order modified Starobinsky inflation

f(R,∇μ1R,…,∇
Cuzinatto
¹
,
Melo
²
,
Medeiros
³

et al. 2019
Phys. Rev. D
16
0
4
0
View full text Add to dashboard Cite

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Deforming the Starobinsky model in ghost-free higher derivative supergravities

Cited by 10 publications

References 100 publications

Multi-field inflation from a higher derivative N = 1 Supergravity model

Multi-field inflation from a higher derivative N = 1 Supergravity model

Higher-order modified Starobinsky inflation

f(R,∇μ1R,…,∇Cuzinatto1, Melo2, Medeiros3 et al. 2019Phys. Rev. D16040View full textAdd to dashboardCite

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f(R,∇μ1R,…,∇
Cuzinatto
¹
,
Melo
²
,
Medeiros
³

et al. 2019
Phys. Rev. D
16
0
4
0
View full text Add to dashboard Cite