We study the possibility that axion Peccei-Quinn symmetry is spontaneously broken after beginning of inflation. This scenario interpolates between preinflationary and postinflationary cosmology with significant phenomenological differences from both. Since not present at early stages inflation large inflationary fluctuations are produced only scales constrained by cosmic microwave background (C...

Purely geometrical arguments show that there exist classes of homospectral inflationary cosmologies, i.e., different expansion histories producing the same spectrum comoving curvature perturbations. We develop a general algorithm to reconstruct potential minimally coupled single scalar fields from an arbitrary history. apply it obtain corresponding potentials, providing numerical and analytical...