  O'Hern, Silbert, Liu and Nagel [Phys. Rev. E. 68, 011306 (2003)] (OSLN) claim
that a special point $J$ of a "jamming phase diagram" (in density, temperature,
stress space) is related to random close packing of hard spheres, and that it
represents, for their suggested definitions of jammed and random, the recently
introduced maximally random jammed state. We point out several difficulties
with their definitions and question some of their claims. Furthermore, we
discuss the connections between their algorithm and other hard-sphere packing
algorithms in the literature.
