We study gravitational wave production in an expanding Universe during the first stages following inflation, and investigate the consequences of the Gauss–Bonnet term on the inflationary parameters for a power-law inflation model with a GB coupling term. Moreover, we perform the analyses on the preheating parameters involving the number of e-folds $$N_{pre}$$
N
pre
, and the temperature of thermalization $$T_{th},$$
T
th
,
and show that it’s sensitive to the parameters n, and $$\gamma $$
γ
, the parameter $$\gamma $$
γ
is proposed to connect the density energy at the end of inflation to the preheating energy density. We set a correlation of gravitational wave energy density spectrum with the spectral index $$n_{s}$$
n
s
detected by the cosmic microwave background experiments. The density spectrum $$\varOmega _{gw}$$
Ω
gw
shows good consistency with observation for $$\gamma =$$
γ
=
$$10^{3}$$
10
3
and $$10^{6}$$
10
6
. Our findings suggest that the generation of gravitational waves (GWs) during preheating can satisfy the constraints from Planck’s 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].
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.
We study a supergravity D-term chaotic inflationary model, in the context of the braneworld scenario, in particular we consider the Randall—Sundrum model type 2. Using the latest release from the combination of WMAP9, eCMB, BAO, and H0, we show that the inflation observables depend only on the number of e-folds N. We also derive all known spectrum inflationary parameters, which are widely consistent with WMAP9 data for a particular choice of values N specially for the scalar spectral index ns and the ratio r. However, the running of the scalar spectral index dns/dlnk is now excluded from the range given by the latest observational measurements.
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