Heavy decaying dark matter at future neutrino radio telescopes
  In the next decades, ultra-high-energy neutrinos in the EeV energy range will
be potentially detected by next-generation neutrino telescopes. Although their
primary goals are to observe cosmogenic neutrinos and to gain insight into
extreme astrophysical environments, they can also indirectly probe the nature
of dark matter. In this paper, we study the projected sensitivity of up-coming
neutrino radio telescopes, such as RNO-G, GRAND and IceCube-gen2 radio array,
to decaying dark matter scenarios. We investigate different dark matter
decaying channels and masses, from $10^7$ to $10^{15}$ GeV. By assuming the
observation of cosmogenic or newborn pulsar neutrinos, we forecast conservative
constraints on the lifetime of heavy dark matter particles. We find that these
limits are competitive with and highly complementary to previous
multi-messenger analyses.
