DESY Theory Seminar
Gravitational waves from the fragmentation of axion-like particle dark matter
by Aleksandr Chatrchyan (U Heidelberg)
Monday, May 25, 2020 from to (Europe/Berlin)
Light scalar bosons, such as axion-like particles (ALP), are appealing candidates for dark matter if produced nonthermally via the vacuum misalignment mechanism. In certain cases, such as in the presence of a monodromy, the self-interactions of ALPs can be sufficiently strong and lead to the fragmentation of the homogeneous field soon after the onset of oscillations. The resulting large inhomogeneities can lead to the production of gravitational waves (GWs). We investigate the nonlinear dynamics of fragmentation, as well as of the subsequent turbulent regime, and calculate the stochastic GW background that is produced from this process. The GW background can be enhanced if the time evolution features an extended intermediate phase of ultrarelativistic dynamics due to a small mass at the bottom of the potential. Yet, this enhancement is limited by the requirement that the dark matter remains sufficiently cold. In some cases the resulting GWs may be within reach of future GW detectors, allowing a complementary probe of this type of dark matter.