Effect of brane tension on reheating parameters in small field inflation according to Planck-2018 data

We study a new reheating approach in the framework of standard and braneworld inflation. Using the technique developed in Ref. 1, we consider a small field arctangent potential and show that this approach can be similarly applied within Randall–Sundrum type 2 scenario and provide additional constraints to reheating temperature [Formula: see text] and duration of reheating [Formula: see text]. We found that in brane case the effective equation-of-state parameter [Formula: see text] must be close to 1, to satisfy Planck-2018 joint constraints on [Formula: see text].

$$\alpha $$-attractor from superconformal E-models in brane inflation

In the large extra dimensional braneworld inflation, Friedmann equation is modified to include a quadratic term in energy density with an additional parameter $$\lambda $$λ called brane tension in addition to the usual linear term. The high energy brane corrections modify the slow-roll parameters and affect the behaviour of inflation. We analyse the superconformal inflation for E-models and find that there exist $$\alpha $$α-attractors in brane inflation. The predictions for the scalar spectral index $$n_s$$ns and the tensor-to-scalar ratio r are computed numerically, and approximate analytic formulas in the high energy limit have been given for the observable $$n_s$$ns and r. The constraints on the model parameters are obtained by using Planck 2018 and BICEP2 observational data.

Observational constraints on reheating in braneworld inflation

The reheating era after inflation is analyzed in the framework of the braneworld models. We study reheating by calculating the reheating temperature in a braneworld inflation for various cosmological parameters. The variation of reheating [Formula: see text]-folding number and reheating temperature were obtained and analyzed as function of a spectrum of perturbation for a polynomial potential [Formula: see text]. We have applied the slow-roll approximation in the high energy limit to constraint the parameter potentials by confronting our results to recent Planck 2018 observations. We have shown that in general the best values of the predicted reheating temperature is of the order [Formula: see text] GeV, with a brane tension [Formula: see text] GeV4. We have also shown that the polynomial potential in the case [Formula: see text] provides the best fit results with recent observational constraints.