  We perform numerical simulations to explore the dynamical evolution of the HD
82943 planetary system. By simulating diverse planetary configurations, we find
two mechanisms of stabilizing the system: the 2:1 mean motion resonance between
the two planets can act as the first mechanism for all stable orbits. The
second mechanism is a dynamical antialignment of the apsidal lines of the
orbiting planets, which implies that the difference of the periastron
longitudes $\theta_{3}$ librates about $180^{\circ}$ in the simulations. We
also use a semi-analytical model to explain the numerical results for the
system under study.
