Power spectrum for perturbations in an inflationary model for a closed universe

We derive the power spectrum of primordial quantum fluctuations in an inflationary universe for curvature parameter $${\mathcal {K}}=1$$K = 1 . This is achieved through a Born–Oppenheimer type of approximation scheme from the Wheeler–DeWitt equation of canonical quantum gravity using gauge-invariant variables. Compared to the flat model, the closed model exhibits a deficit of power at large scales.