Common Origin of $3.55$ keV X-ray line and Gauge Coupling Unification
  with Left-Right Dark Matter
  We present a minimal left-right dark matter framework that can simultaneously
explain the recently observed 3.55 keV X-ray line from several galaxy clusters
and gauge coupling unification at high energy scale. Adopting a minimal dark
matter strategy, we consider both left and right handed triplet fermionic dark
matter candidates which are stable by virtue of a remnant $\mathcal{Z}_2\simeq
(-1)^{B-L}$ symmetry arising after the spontaneous symmetry breaking of
left-right gauge symmetry to that of the standard model. A scalar bitriplet
field is incorporated whose first role is to allow radiative decay of right
handed triplet dark matter into the left handed one and a photon with energy
3.55 keV. The other role this bitriplet field at TeV scale plays is to assist
in achieving gauge coupling unification at a high energy scale within a
non-supersymmetric $SO(10)$ model while keeping the scale of left-right gauge
symmetry around the TeV corner. Apart from solving the neutrino mass problem
and giving verifiable new contributions to neutrinoless double beta decay and
charged lepton flavour violation, the model with TeV scale gauge bosons can
also give rise to interesting collider signatures like diboson excess, dilepton
plus two jets excess reported recently in the large hadron collider data.
