Testing Einstein's Equivalence Principle with Cosmological Fast Radio
  Bursts behind Clusters of Galaxies
  Aims: Recently, cosmological fast radio bursts (FRBs) have been used to
provide the most stringent limit up to date on Einstein's Equivalence Principle
(EEP). We study how to further test EEP with FRBs. Methods: Future systematic
radio surveys will certainly find abundant FRBs at cosmological distances and
some of them will inevitably be located behind clusters of galaxies. Here we
suggest to use those FRBs to further test EEP. Results: We find that the
robustness and accuracy of testing EEP can be improved further by orders of
magnitude with these FRBs. The same methodology can also be applied to any
other types of fast and bright transients at cosmological distances.
