Upgrading Sterile Neutrino Dark Matter to FI$m$P Using Scale Invariance
  In this article we propose a class of extremely light feebly interacting
massive particle, FI$m$Ps. They are combination of feebly interacting massive
particle with scale invariance, by which DM stability, mass origin and relic
density are inherently related. In the scale invariant version of the Standard
Model (SM) with three right-handed neutrinos ($\nu$SISM), the lightest $N_1$
realizes the FI$m$P scenario. In this example scalar singlets, which are
intrinsic to the $\nu$SISM, generate mass and relic density for this FI$m$P
simultaneously. Moreover, they are badly needed for electroweak symmetry
spontaneously breaking. Interestingly, a 7.1 keV $N_1$ with correct relic
density, that can explain the recent 3.55 keV $X-$ray line, lies in the bulk
parameter space of our model.
