Constraining scalar-Gauss-Bonnet inflation by reheating, unitarity, and Planck data

Abstract

We revisit the inflationary dynamics in detail for theories with Gauss-Bonnet gravity coupled to scalar functions, in light of the Planck data. Considering the chaotic inflationary scenario, we constrain the parameters of two models involving inflaton-Gauss-Bonnet coupling by current Planck data. For non zero inflaton-Gauss-Bonnet coupling β, an inflationary analysis provides us a big cosmologically viable region in the space of (m, β), where m is the mass of inflaton. However, we study further on constraining β arising from reheating considerations and unitarity of tree-level amplitude involving we have studied the constraints on β arising from reheating considerations and unitarity of tree level amplitude involving 2 graviton → 2 graviton (hh → hh) scattering. Our analysis, particularly on reheating significantly reduces the parameter space of (m, β) for all models. he quadratic Gauss-Bonnet coupling parameter turns out to be more strongly constrained than that of the linear coupling. For the linear Gauss-Bonnet coupling function, we obtain β 10 3 , with the condition β(m/M P ) 2

Gauss–Bonnet term corrections in scalar field cosmology

“…The evolution of cosmological perturbations and their corresponding parameters for Einstein-Gauss-Bonnet (EGB) inflationary models were considered in papers [43][44][45][46][47][48][49][50][51][52]. In this case, it should be noted that the non-minimal coupling of a scalar field and the Gauss-Bonnet scalar allows to verify cosmological inflationary models from observational constraints on the values of cosmological perturbation parameters [53,54], in contrast to some models constructed based on Einstein gravity only due to difference in the evolution of perturbations at the inflationary stage [31,44,45,48,49].…”

Constraints on the reheating parameters after Gauss-Bonnet inflation from primordial gravitational waves

“…Therefore, in this work, we consider inflationary models with a Gauss-Bonnet (GB) term to estimate the energy spectrum of the PGW and to provide constraints on the reheating parameters. Inflationary models with a GB term are not uncommon, and it is well studied in the context of inflation, dark energy, and the PGW [28][29][30][31][32][33][34][35][36], as well as for reheating [37][38][39].…”

“…(38) for model I (dashed black line) and model II (green line) in comparison with Eq. (2.16) of Ref.…”

Revisiting slow-roll dynamics and the tensor tilt in general single-field inflation

“…We substitute the assumed form of the Horndeski functions G a [Eq. (24)] to the general formulas of the quadratic action for cosmological perturbations derived in Ref. [4].…”

“…While the argument in [9] seems to be general to a large extent, a counterexample is known to exist in the literature: inflation with the nonminimal coupling to the Gauss-Bonnet term [18][19][20][21][22][23][24][25][26][27][28][29]. Though in this case the energy density of the slowly rolling inflaton is dominated by its potential, one can have a positive tensor tilt [18,19,22].…”