4.4 “End of Inflation” Mechanism 60 of thermal inflation reheating, as this value corresponds to the number of relativistic degrees of freedom in the Standard Model. The definition of the Tensor Fraction, r [1], is where P h and P ζ are the spectrums of the primordial tensor and curvature perturbations respectively. The spectrum P h is given by In this section, we investigate the “end of inflation” mechanism. We aim to obtain a number of constraints on the model parameters and the initial con- ditions for the fields. Considering these constraints, we intend to determine the available parameter space (if any). In this parameter space we will cal- for a given wavenumber k . Using this, together with $^{ρ}$∗ =3 M 2 $_{P}$H 2 ∗ , given that we are saying H$_{k}$ = $^{H}$∗ for our current case, as well as the observed value P $_{ζ}$( k$_{0}$ )=2 . 142 × 10 − $^{9}$, we obtain 4.3.3 Tensor Fraction r r ≡ P h ζ (4.53) P $_{h}$( k ) = 8 M 2 P ( H$_{k}$ 2 π ) 2 (4.54) r =   ρ$^{1}$ 4 ∗ 3 . 25 × 10 16 $_{GeV}$ $^{4}$ (4.55) 4.4 “End of Inflation” Mechanism