Width of the 511 KeV Line from the Bulge of the Galaxy
  In this paper I present the detail estimations for the width of the 511 keV line produced by a mechanism when dark matter is represented by macroscopically large dense nuggets. I argue that the width of 511 keV emission in this mechanism is very narrow (in a few keV range) in agreement with all observations. The dominant mechanism of the annihilation in this case is the positronium formation e^+e^-to ^1S_0 to 2\gamma rather than a direct e^+e^- to 2\gamma$ annihilation. I also discuss some generic features of the \gamma rays spectrum (in few MeV range) resulting from this mechanism. 
Ariel Zhitnitsky