Spectrum of Cosmological Perturbations from Multiple-Stage Inflation
  Within the context of supersymmetric hybrid inflation, we study a multiple-stage inflationary scenario that can generate a primordial spectrum of adiabatic density perturbations with a break at $k_b \simeq 0.05 h Mpc^{-1}$. The presence of such a break is supported by the APM galaxy survey data. We consider a specific model within this scenario and confront it with observational data. We reproduce the angular power spectrum of CMB anisotropies, and also account for the break in the power spectrum of galaxy clustering. In addition, we find a value for $\sigma_8$ in agreement with the one deduced from observations. A characteristic property of the spectrum is a drop of the spectral index from $n \simeq 1$ to $n \sim 0.6$ at $k \sim k_b$. 
Mairi Sakellariadou and Nikos Tetradis