Lattice Simulations of Axion-U(1) Inflation
  If gauge fields are coupled to an axion field during inflation, they can lead
to unique observational signatures. However, this system often shows strong
backreaction effects, invalidating the standard perturbation theory approach.
In this work, we present the first nonlinear lattice simulation of an
axion-U(1) system during inflation. We use it to fully characterize the
statistics of the comoving curvature perturbation $\zeta$. We find that
non-Gaussianity of $\zeta$ is large in the linear regime, whereas it is
suppressed when the dynamics becomes nonlinear. This relaxes bounds from
overproduction of primordial black holes, allowing for an observable
gravitational waves signal at interferometer scales.
