The probability of large primordial scalar perturbations (leading to primordial black hole formation and the concurrent GW backgrounds) is sensitive to the tail of the PDF of primordial curvature perturbations. We analyse such tails in inflationary models featuring an ultra slow-roll phase, known to enhance both the amplitude and non-Gaussianity of curvature perturbations at small scales. We...
Effective field theories (EFTs) parametrize our ignorance of the underlying UV theory through their Wilson coefficients. However, not all values of these coefficients are consistent with fundamental physical principles. In this paper, we explore the consequences of imposing causal propagation on the comoving curvature perturbation in the EFT of inflation, particularly its impact on the...
Both single- and multi-field models of inflation might lead to enhanced scalar fluctuations on scales much smaller than those seeding the large-scale structure formation. In these scenarios, it is possible that the spike of power at high wavenumber might induce large corrections to the scalar power spectrum, e.g. in the form of loop corrections, potentially endangering the perturbativity of...
Inflationary models with an inflection point potential may produce a significant abundance of primordial black holes. I show that in typical models, inflation is eternal near the inflection point, that is, the volume of the inflating region diverges at late times. The inflating space then has a fractal structure, with eternal inflation taking place inside type II black holes. I discuss the...
Quantum fluctuations during inflation in the very early universe inevitably generate inhomogeneities and anisotropies across all observable scales and beyond. In the stochastic approach to modeling inflationary dynamics, these quantum fluctuations are incorporated as stochastic noise. We employ the formalism of stochastic inflation to examine the role of quantum diffusion during inflation....
