Left Right Symmetric Models with a Mixture of keV-TeV Dark Matter
  We discuss the possibility of realising a multi-component dark matter
scenario with widely separated dark matter masses: one having keV scale mass
and the other with GeV-TeV scale mass, within the framework of left right
symmetric models. Due to gauge interactions, both the dark matter candidates
are produced thermally in the early Universe but overproducing the keV mass
candidate. We consider one of the right handed neutrinos to be decaying at late
epochs, just before the big bang nucleosynthesis, in order to dilute the
thermally overproduced keV dark matter. We constrain the parameter space from
the requirement of producing sub-dominant keV-TeV dark matter, satisfying
indirect detection constraints from gamma ray searches and producing the
tantalising 3.55 keV monochromatic X-ray line, reported by several groups to be
present in galaxy and galaxy cluster data, from the decay of a 7.1 keV dark
matter on cosmological scales. We find that these requirements can keep the
right sector gauge boson masses around a few TeV while requiring some of the
right-handed neutrinos in the sub-GeV regime.
