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تسجيل مستخدم جديدSub-Planckian $phi^{2}$ Inflation in the Palatini Formulation of Gravity with an $R^2$ term
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In the context of the Palatini formalism of gravity with an $R^{2}$ term, a $phi^{2}$ potential can be consistent with the observed bound on $r$ whilst retaining the successful prediction for $n_{s}$. Here we show that the Palatini $phi^{2} R^2$ inflation model can also solve the super-Planckian inflaton problem of $phi^{2}$ chaotic inflation, and that the model can be consistent with Planck scale-suppressed potential corrections. If $alpha gtrsim 10^{12}$, where $alpha$ is the coefficient of the $R^2$ term, the inflaton in the Einstein frame, $sigma$, remains sub-Planckian throughout inflation. In addition, if $alpha gtrsim 10^{20}$ then the predictions of the model are unaffected by Planck-suppressed potential corrections in the case where there is a broken shift symmetry, and if $alpha gtrsim 10^{32}$ then the predictions are unaffected by Planck-suppressed potential corrections in general. The value of $r$ is generally small, with $r lesssim 10^{-5}$ for $alpha gtrsim 10^{12}$. We calculate the maximum possible reheating temperature, $T_{R;max}$, corresponding to instantaneous reheating. For $alpha approx 10^{32}$, $T_{R; max}$ is approximately $10^{10}$ GeV, with larger values of $T_{R;max}$ for smaller $alpha$. For the case of instantaneous reheating, we show that $n_{s}$ is in agreement with the 2018 Planck results to within 1-$sigma$, with the exception of the $alpha approx 10^{32}$ case, which is close to the 2-$sigma$ lower bound. Following inflation, the inflaton condensate is likely to rapidly fragment and form oscillons. Reheating via inflaton decays to right-handed neutrinos can easily result in instantaneous reheating. We determine the scale of unitarity violation and show that, in general, unitarity is conserved during inflation.
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