On Viability of Inflation in Nonminimal Kinetic Coupling Theory

Avdeev, N. A.; Toporensky, A. V.

doi:10.1134/s0202289321030038

Cited by 10 publications

(2 citation statements)

References 22 publications

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“…The dynamics of negative κ is much richer and includes, for example, such an exotic possibility as realising inflation without a scalar field potential [34]. This regime requires large φ [35], and hence, can not be described by the usual slow-roll approximations. We leave the case of negative κ for a future work.…”

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confidence: 99%

Ruling out an inflation driven by a power law potential: kinetic coupling does not help

Avdeev¹,

Toporensky²

2022

Preprint

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We demonstrate that the latest constraints on inflationary observables, namely the tensor-toscalar ratio r and the scalar spectral index n S , from the Cosmic Background Radiation (CMB) observations are already strong enough to rule out the model of a scalar field kinetically coupled to gravity with a positive coupling constant and a power law potential. The case for a negative coupling constant needs special treatment.

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confidence: 99%

Ruling out an inflation driven by a power law potential: kinetic coupling does not help

Avdeev¹,

Toporensky²

2022

Preprint

Self Cite

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“…Higgs-like potential and exponential potential have been investigated. Recent work [66] considers n = 1.5, reasonable (i.e. sub-Planckian) initial field value can give sufficient e-folding number for the solving the horizon problem with large value of coupling and a very small scalar mass.…”

Section: Introductionmentioning

confidence: 99%

Cosmology in holographic non-minimal derivative coupling theory: constraints from inflation and variation of gravitational constant

Phichayoot¹,

Gumjudpai²,

Kritpetch³

et al. 2022

Preprint

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We consider a cosmological model of non-minimal derivative coupling (NMDC) to gravity with holographic effect from Bekenstein-Hawking entropy using Hubble horizon IR cutoff. Holographic parameter c is considered constant with value in a range, 0 ≤ c < 1. The NMDC effect is considered either as modification in kinetic scalar field or in gravitational constant. The NMDC effect allows gravitational constant to be time-varying. Since the NMDC effect is cosmological, definition of holographic density should include time-varying part of the gravitational constant. The NMDC part reduces strength of gravitational constant for κ > 0 and opposite for κ < 0. The holographic part enhances gravitational strength. Slow-roll parameters are derived. We use spectral index and tensor-to-scalar ratio to test the model against CMB constraint. Number of e-folding is chosen to be N ≥ 60. Power-law scalar potentials, V = V0φ n with n = 2, 4, and exponential potential, V = V0 exp (−βφ) are considered. Combined parametric plots of κ and φ show that the allowed regions of the power spectrum index and of the tensor-to-scalar ratio are not overlapping. NMDC inflation is ruled out and the holographic NMDC inflation is also ruled out for 0 < c < 1. NMDC significantly changes major anatomy of the dynamics, i.e. it gives new late-time attractor trajectories in acceleration regions. The holographic part clearly affects pattern of trajectories. However, for the holographic part to affect shape of the acceleration region, the NMDC field must be in presence. To constrain the model at late time, variation of gravitational constant is considered. Gravitationalwave standard sirens and supernovae data give a constraint, Ġ/G|t 0 < ∼ 3 × 10 −12 year −1 [142] which, for this model, results in 10 −12 year −1 > ∼ −κ φ φ/M 2 P . Positive κ is favored and greater c 2 results in lifting up lower bound of κ.

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Cosmology in holographic non-minimal derivative coupling theory: Constraints from inflation and variation of gravitational constant

Phichayoot

Gumjudpai

Kritpetch

et al. 2023

Physics of the Dark Universe

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On Viability of Inflation in Nonminimal Kinetic Coupling Theory

Cited by 10 publications

References 22 publications

Ruling out an inflation driven by a power law potential: kinetic coupling does not help

Ruling out an inflation driven by a power law potential: kinetic coupling does not help

Cosmology in holographic non-minimal derivative coupling theory: constraints from inflation and variation of gravitational constant

Cosmology in holographic non-minimal derivative coupling theory: Constraints from inflation and variation of gravitational constant

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