**1-d granular gas with little dissipation in
0-g : A comment on "Resonance oscillations in Granular gases"**

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**Abstract:
**It is demonstrated that recent
results on 1d granular gas in a container with a vibrating piston, which was
modelled by a shock wave propagation, can be understood with a modelling using
ideas coming from the "thermodynamics of a single particle". Defining
e as the square root of the energetic-restitution coefficient of a single
collision, the mean loss during a round trip of the momentum is calculated in
the limit N(1-e)<<1. It is also demonstrated that the system cannot
propagate sound waves nor shock waves in the limit of N(1-e)<<1 and that
hydrodynamics equations cannot be defined when N(1-e)<<1.

**Pacs # : **5.40 ; 45.70 ; 62.20 ; 83.70.Fn

*poudres & grains* **12** (3), 50-59 (April 2 001)