Damping of gravitational waves in 2-2-holes

A 2-2-hole is an explicit realization of a horizonless object that can still very closely resemble a BH. An ordinary relativistic gas can serve as the matter source for the 2-2-hole solution of quadratic gravity, and this leads to a calculable area-law entropy. Here we show that it also leads to an estimate of the damping of a gravitational wave as it travels to the center of the 2-2-hole and back out again. We identify two frequency dependent effects that greatly diminish the damping. Spinning 2-2-hole solutions are not known, but we are still able to consider some spin dependent effects. The frequency and spin dependence of the damping helps to determine the possible echo resonance signal from the rotating remnants of merger events. It also controls the fate of the ergoregion instability.