Dark Matter and the XENON1T electron recoil excess
  We show that the electron recoil excess around 2 keV claimed by the Xenon
collaboration can be fitted by DM or DM-like particles having a fast component
with velocity of order $\sim 0.1$. Those particles cannot be part of the cold
DM halo of our Galaxy, so we speculate about their possible nature and origin,
such as fast moving DM sub-haloes, semi-annihilations of DM and relativistic
axions produced by a nearby axion star. Feasible new physics scenarios must
accommodate exotic DM dynamics and unusual DM properties.
