Non-minimally gravity-coupled inflationary models

Physical Review D, 1999

In higher-curvature inflation models (R + αnR n ), we study a parametric preheating of a scalar field χ coupled non-minimally to a spacetime curvature R (ξRχ 2 ). In the case of R 2 -inflation model, efficient preheating becomes possible for rather small values of ξ, i.e. |ξ| < ∼ several. Although the maximal fluctuation χ 2 max ≈ 2×10 17 GeV for ξ ≈ −4 is almost the same as the chaotic inflation model with a non-minimally coupled χ field, the growth rate of the fluctuation becomes much larger and efficient preheating is realized. We also investigate preheating for R 4 model and find that the maximal fluctuation is

Journal of Cosmology and Astroparticle Physics, 2011

We show how we can implement chaotic inflation in the context of supergravity by conveniently selecting the functional form of a strong enough non-minimal coupling between the inflaton and the Ricci scalar curvature. The procedure can be applied when a gauge singlet or non-singlet inflaton is coupled to another singlet superfield within linear-quadratic, trilinear or bilinear superpotential terms. The tachyonic instability occurring along the direction of the accompanying non-inflaton field can be cured by expanding the kinetic part of the frame function up to the fourth order in powers of the various fields. In the case of a gauge non-singlet inflaton, though, a conjugation symmetry has to be imposed on these terms in order for the flatness of the inflationary potential is maintained. On the other hand, some of these terms assist us to precisely reconcile the resulting scalar spectral index with the current PLANCK measurements while the other inflationary observables are in agreeme...

In this paper, we investigate chaotic inflation from scalar field subjected to potential in the framework of f (R 2 , P, Q)-gravity, where we add a correction to Einstein's gravity based on a function of the square of the Ricci scalar R 2 , the contraction of the Ricci tensor P , and the contraction of the Riemann tensor Q. The Gauss-Bonnet case is also discussed. We give the general formalism of inflation, deriving the slow-roll parameters, the e-folds number, and the spectral indexes. Several explicit examples are furnished, namely we will consider the cases of massive scalar field and scalar field with quartic potential and some power-law function of the curvature invariants under investigation in the gravitational action of the theory. Viable inflation according with observations is analyzed. * data, the choice of the models is quite large (see Refs. [5, for an introduction to inflationary cosmology).

Phys.Rev. D105 (2022) 043514, 2022

We consider a modified gravity framework for inflation by adding to the Einstein-Hilbert action a direct f(ϕ)T term, where ϕ is identified as the inflaton and T is the trace of the energy-momentum tensor. The framework goes to Einstein gravity naturally when the inflaton decays out. We investigate inflation dynamics in this f(ϕ)T gravity (not to be confused with torsion-scalar coupled theories) on a general basis and then apply it to three well-motivated inflationary models. We find that the predictions for the spectral tilt and the tensor-to-scalar ratio are sensitive to this new f(ϕ)T term. This f(ϕ)T gravity brings chaotic and natural inflation into better agreement with data and allows a larger tensor-to-scalar ratio in the Starobinsky model.

Physical Review D, 2015

We consider Supersymmetric (SUSY) and non-SUSY models of chaotic inflation based on the φ n potential with 2 ≤ n ≤ 6. We show that the coexistence of a non-minimal coupling to gravity fR = 1 + cRφ n/2 with a kinetic mixing of the form fK = cKf m R can accommodate inflationary observables favored by the BICEP2/Keck Array and Planck results for 0 ≤ m ≤ 4 and 2.5 • 10 −4 ≤ rRK = cR/c n/4 K ≤ 1, where the upper limit is not imposed for n = 2. Inflation can be attained for subplanckian inflaton values with the corresponding effective theories retaining the perturbative unitarity up to the Planck scale.

We discuss, in the context of N = 1 hidden sector non-minimal supergravity chaotic inflationary models, constraints on the parameters of a polynomial superpotential resulting from existing bounds on the reheating temperature and on the amplitude of the primordial energy density fluctuations as inferred from COBE. We present a specific two-parameter chaotic inflationary model which satisfies these constraints and discuss a possible scenario for adequate baryon asymmetry generation.

2020

In this paper, we investigate the potential-driven inflation models with a disformal coupling to Einstein gravity, to find out the effects of such a coupling on these models. We consider a simple coupling form which introduces only one parameter, and three inflation models, namely the chaotic inflation, the Higgs inflation, and the monodromy inflation. We find that the disformal coupling can have some modifications to the observational variables of these models such as the power spectrum, the spectral index as well as the tensor/scalar ratio, although not too large due to the constraints on the disformal coupling parameter. With these modifications, one has the opportunity of improving models that lie on the edge of the favorable regions of Planck observational data, such as monodromy inflation. Moreover, the nontrivial sound speed of tensor perturbations (gravitational waves) may come out, due to the coupling of gravity and kinetic terms of the field.

2014

We study the polynomial chaotic inflation model with a single scalar field in a double well quartic potential which has recently been shown to be consistent with Planck data. In particular, we study the effects of lifting the degeneracy between the two vacua on the inflationary observables, i.e., spectral index n s and tensor-to-scalar perturbation ratio r T. We find that removing the degeneracy allows the model to satisfy the upper limit constraints on r T from Planck data, provided the field starts near the local maximum. We also calculate the scalar power spectrum and non-Gaussianity parameter f NL for the primordial scalar perturbations in this model.

arXiv: Cosmology and Nongalactic Astrophysics, 2016

With the growing consensus on simple power law inflation models not being favored by the PLANCK observation, dynamics for the non-standard form of the inflaton potential gain significant interest in the recent past. In this paper, we analyze in great detail classes of phenomenologically motivated inflationary models with non-polynomial potential which are the generalization of the potential introduced in \cite{mhiggs}. After the end of inflation, inflaton field will coherently oscillate around its minimum. Depending upon the initial amplitude of the oscillation and coupling parameters standard parametric resonance phenomena will occur. Therefore, we will study how the inflationary model parameters play an important role in understanding the resonant structure of our model under study. Subsequently, the universe will go through the perturbative reheating phase. However, without any specific model consideration, we further study the constraints on our models based on model independent...