A review on radiation of oscillons and oscillatons

Numerical simulations show that a massive real scalar field in a nonlinear theory can form long-lived oscillating localized states. For a self-interacting scalar on a fixed background these objects are named oscillons, while for the self-gravitating case they are called oscillatons. This extensive review is about the history and various general properties of these solutions, though mainly focusing on the small but nonzero classical scalar field radiation emitted by them. The radiation for higher amplitude states can be calculated by a spectral numerical method. For small and moderately large amplitudes an analytical approach based on complex extension, asymptotic matching and Borel summation can be used. This procedure for the calculation of the energy loss rate is explained in a detailed way in this review, starting with the simplest one-dimensional scalar oscillons at first, and reaching to $3+1$ dimensional self-gravitating oscillatons based on that experience.