The 3.5 keV X-ray line signal from decaying moduli with low cutoff scale
  The recent unidentified 3.5 keV X-ray line signal can be explained by decaying moduli dark matter with a cutoff scale one order of magnitude smaller than the Planck scale. We show that such modulus field with the low cutoff scale follows a time-dependent potential minimum and its abundance is reduced by the adiabatic suppression mechanism. As a result the modulus abundance can naturally be consistent with the observed dark matter abundance without any fine-tuning of the initial oscillation amplitude. 
Kazunori Nakayama, Fuminobu Takahashi, Tsutomu T. Yanagida
hep-ph astro-ph.CO astro-ph.HE