Adiabatic regularisation of power spectra in nonminimally coupled chaotic inflation

We investigate the effect of adiabatic regularization on both the tensor- and scalar-perturbation power spectra in $\mathit{\text{nonminimally}}$ coupled chaotic inflation. Similar to that of the $\mathit{\text{minimally}}$ coupled general single-field inflation, we find that the subtraction term is suppressed by an exponentially decaying factor involving the number of $e$-folds. By following the subtraction term long enough beyond horizon crossing, the regularized power spectrum tends to the “bare” power spectrum. This study justifies the use of the unregularized (“bare”) power spectrum in standard calculations.