On cosmological Inflation In Palatini F(R,ϕ)F(R,\phi) Gravity

Single field inflationary models are investigated within Palatini quadratic gravity represented by $R+\alpha R^2$ along with a non-minimal coupling of the form $f(\phi) R$ between the inflaton field $\phi$ and the gravity. The treatment is performed in the Einstein frame, where the minimal coupling to gravity is recovered through conformal transformation. We consider various limits of the model with different inflationary scenarios characterized as canonical slow-roll inflation in the limit $\alpha \dot{\phi}^2\ll (1+f(\phi))$, constant-roll k-inflation for $\alpha \ll 1$, and slow-roll K-inflation for$\alpha \gg 1$ . A cosine and exponential potential are examined with the limits mentioned above and different well-motivated non-minimal couplings to gravity. We compare the theoretical results, exemplified by the tensor-to-scalar $r$ ratio and spectral index $n_s$, with the recent observational results of Planck 2018 $\&$ BICEP/Keck . Furthermore, we include the results of a new study forecast precision with which $n_s$ and $r$ can be constrained by currently envisaged observations, including CMB (Simons Observatory, CMB-S4, and LiteBIRD)Comment: 6 pages, 1 figure, 3 tables. version to appear in Physical Sciences Forum as a Contribution to: 2nd Electronic Conference on Universe,202

Warm Affine Inflation

The warm inflationary scenario is investigated in the context of affine gravity formalism. A general framework is provided for studying different single-field potentials. Using the sphaleron mechanism we explain the continuous dissipation of the inflaton field into radiation, leading to the $\Gamma=\Gamma_0 T^3$ dissipation coefficient. The treatment is performed in the weak and strong dissipation limits. We consider the quartic potential as a case study to provide a detailed study. Moreover, in this study, we discuss various constraints on inflationary models in general. We compare the theoretical results of the quartic potential model within warm inflation with the observational constraints from Planck $2018$ and BICEP/Keck 2018, as presented by the tensor-to-scalar ratio, spectral index and the perturbation spectrum.Comment: 21 pages, 5 figures, 4 table

On Cosmological Inflation in Palatini F(R,ϕ) Gravity

Single field inflationary models are investigated within Palatini quadratic gravity, represented by R+αR2, along with a non-minimal coupling of the form f(ϕ)R between the inflaton field ϕ and the gravity. The treatment is performed in the Einstein frame, where the minimal coupling to gravity is recovered through conformal transformation. We consider various limits of the model with different inflationary scenarios characterized as canonical slow-roll inflation in the limit αϕ˙2≪(1+f(ϕ)), constant-roll k-inflation for α≪1, and slow-roll K-inflation for α≫1. A cosine and exponential potential are examined with the limits mentioned above and different well-motivated non-minimal couplings to gravity. We compare the theoretical results, exemplified by the tensor-to-scalar r ratio and spectral index ns, with the recent observational results of Planck 2018 and BICEP/Keck. Furthermore, we include the results of a new study forecast precision with which ns and r can be constrained by currently envisaged observations, including CMB (Simons Observatory, CMB-S4, and LiteBIRD)

Palatini f(R) Gravity and Variants of k-/Constant Roll/Warm Inflation within Variation of Strong Coupling Scenario

We show that upon applying Palatini f(R), characterized by an αR2 term, within a scenario motivated by a temporal variation of strong coupling constant, then one obtains a quadratic kinetic energy. We do not drop this term, but rather study two extreme cases: α<<1 and α>>1. In both cases, one can generate a kinematically-induced inflationary paradigm. In order to fit the Planck 2018 data, the α>>1 case, called k-inflation, requires a fine tuning adjustment with nonvanishing nonminimal coupling to gravity parameter ξ, whereas the α<<1 case, studied in the constant-roll regime, can fit the data for vanishing ξ. The varying strong coupling inflation scenario remains viable when implemented through a warm inflation scenario with or without f(R) gravity

On Warm Natural Inflation and Planck 2018 Constraints

We investigate natural inflation with non-minimal coupling to gravity, characterized either by a quadratic or a periodic term, within the warm inflation paradigm during the slow-roll stage, in both strong and weak dissipation limits; and show that, in the case of a T-linearly dependent dissipative term, it can accommodate the spectral index ns and tensor-to-scalar ratio r observables given by Planck 2018 constraints, albeit with a too-small value of the e-folding number to solve the horizon problem, providing, thus, only a partial solution to natural inflation issues, assuming a T-cubically dependent dissipative term can provide a solution to this e-folding number issue

On Warm Natural Inflation and Planck 2018 Constraints

We investigate natural inflation with non-minimal coupling to gravity, characterized either by a quadratic or a periodic term, within the warm inflation paradigm during the slow-roll stage, in both strong and weak dissipation limits; and show that, in the case of a T-linearly dependent dissipative term, it can accommodate the spectral index ns and tensor-to-scalar ratio r observables given by Planck 2018 constraints, albeit with a too-small value of the e-folding number to solve the horizon problem, providing, thus, only a partial solution to natural inflation issues, assuming a T-cubically dependent dissipative term can provide a solution to this e-folding number issue