Generalised inflation with a gravitational wave background
  We propose a Lambda-inflation model which explains a significant part of the COBE signal by primordial cosmic gravitational waves. The primordial density perturbations fulfill both the constraints of large-scale microwave background and galaxy cluster normalization. The model is tested against the galaxy cluster power spectrum and the high-multipole angular CMB anisotropy. 
V.N. Lukash (1), E.V. Mikheeva (1), V. Muller (2) and A.M. Malinovsky   (1) ((1) Astro Space Center of P.N.Lebedev Physical ...