A tail of eternal inflation

Non-trivial inflaton self-interactions can yield calculable signatures of primordial non-Gaussianity that are measurable in cosmic surveys. Surprisingly, we find the phase transition to slow-roll eternal inflation is often incalculable same models. Instead, this sensitive non-Gaussian tail distribution scalar fluctuations, which probes physics inside horizon, potentially beyond cutoff scale Effective Field Theory Inflation. We demonstrate fact directly by calculating corrections Stochastic Inflation within framework Soft de Sitter Theory, from derive associated probability for fluctuations. parameter space consistent with current observations and weak coupling at horizon crossing large fluctuations relevant only be determined appealing a UV completion. also show breakdown perturbative description required entropy reflect number microstates.