Nonlinear Tails of Gravitational Waves in Schwarzschild Black Hole Ringdown

Schwarzschild black holes evolve toward their static configuration by emitting gravitational waves, which decay over time following a power law at fixed spatial positions. We derive this power law analytically for the second-order even gravitational perturbations, demonstrating that it is determined by the fact that the second-order source decays as the inverse square of the distance. Quadratic gravitational modes with multipole $\mathrm{\ell }$ decay according to a law $\sim t^{-2\mathrm{\ell }-1}$, in contrast to the linear Price law scaling $\sim t^{-2\mathrm{\ell }-3}$. Consequently, nonlinear tails may persist longer than their linear counterparts.