Probing Miracle-less WIMP Dark Matter via Gravitational Waves Spectral
  Shapes
  We propose a novel probe of weakly interacting massive particle (WIMP) dark
matter candidates of a wide mass range which fall short of the required
annihilation rates to satisfy correct thermal relic abundance, dubbed as
\textit{Miracle-less WIMP}. If the dark matter (DM) interactions are mediated
by an Abelian gauge boson like B-L, its annihilation rates typically remain
smaller than the WIMP ballpark for very high scale B-L symmetry breaking. The
thermally overproduced WIMP DM is brought within correct relic limits via late
entropy dilution from one of the three right handed neutrinos (RHN) present for
keeping the model anomaly free and generate light neutrino masses. Such late
entropy injection leads to peculiar spectral shapes of gravitational waves (GW)
generated by cosmic strings, formed as a result of B-L symmetry breaking. We
find interesting correlation between DM mass and turning frequency of the GW
spectrum with the latter being within reach of future experiments. The two
other RHNs play major role in generating light neutrino masses and baryon
asymmetry of the universe via leptogenesis. Successful leptogenesis with
Miracle-less WIMP together restrict the turning frequencies to lie only within
the sensitivity limits of future GW experiments like Cosmic Explorer and
Einstein Telescope.
