  The Jamming of soft spheres at zero temperature, the J-point, has been
extensively studied both numerically and theoretically and can now be
considered as a safe location in the space of models, where a street lamp has
been lit up. However, a recent work by Ikeda et al, 2013 reveals that, in the
Temperature/Packing fraction parameter space, experiments on colloids are
actually rather far away from the scaling regime illuminated by this lamp. Is
it that the J-point has little to say about real system? What about granular
media? Such a-thermal, frictional, systems are a-priori even further away from
the idealized case of thermal soft spheres. In the past ten years, we have
systematically investigated horizontally shaken grains in the vicinity of the
Jamming transition. We discuss the above issue in the light of very recent
experimental results. First, we demonstrate that the contact network exhibits a
remarkable dynamics, with strong heterogeneities, which are maximum at a
packing fraction phi star, distinct and smaller than the packing fraction phi
dagger, where the average number of contact per particle starts to increase.
The two cross-overs converge at point J in the zero mechanical excitation
limit. Second, a careful analysis of the dynamics on time scales ranging from a
minute fraction of the vibration cycle to several thousands of cycles allows us
to map the behaviors of this shaken granular system onto those observed for
thermal soft spheres and demonstrate that some light of the J-point street-lamp
indeed reaches the granular universe.
