  Within the transport model evaluation project (TMEP) of simulations for
heavy-ion collisions, the mean-field response is examined here. Specifically,
zero-sound propagation is considered for neutron-proton symmetric matter
enclosed in a periodic box, at zero temperature and around normal density. The
results of several transport codes belonging to two families (BUU-like and
QMD-like) are compared among each other and to exact calculations. For BUU-like
codes, employing the test particle method, the results depend on the
combination of the number of test particles and the spread of the profile
functions that weight integration over space. These parameters can be properly
adapted to give a good reproduction of the analytical zero-sound features.
QMD-like codes, using molecular dynamics methods, are characterized by large
damping effects, attributable to the fluctuations inherent in their phase-space
representation. Moreover, for a given nuclear effective interaction, they
generally lead to slower density oscillations, as compared to BUU-like codes.
The latter problem is mitigated in the more recent lattice formulation of some
of the QMD codes. The significance of these results for the description of real
heavy-ion collisions is discussed.
