  We construct a family of models with negative gravitational mass in the
context of Newtonian gravity. We focus in particular on a model that reproduces
the features of the so-called Dirac-Milne universe, a matter-antimatter
symmetric universe that was recently proposed as an alternative cosmological
scenario [A. Benoit-Levy and G. Chardin, A&A 537, A78 (2012)]. We perform
one-dimensional N-body simulations of these negative-mass models for an
expanding universe and study the associated formation of gravitational
structures. The similarities and differences with the standard cosmological
model are highlighted and discussed.
