Large power spectrum and primordial black holes in the effective theory of inflation

Understand

We study the generation of a large power spectrum, necessary for primordial black hole formation, within the effective theory of single-field inflation.

• The mechanisms we consider include a transition into a ghost-inflation-like phase and scenarios where an exponentially growing mode is temporarily turned on.
• In the cases we discuss, the enhancement in the power spectrum results from either a swift change in some effective coupling or a modification of the dispersion relation for the perturbations, while the background evolution remains unchanged and approximately de Sitter throughout inflation.
• The robustness of the results is guaranteed thanks to a weakly broken galileon symmetry, which protects the effective couplings against large quantum corrections.