▎ 摘　　要

The effect of space symmetry on magnetoplasmon charge density and spin-density excitations in a weakly tunnel coupled bilayer electron system at the filling factor nu = 4 is considered. The optic magnetoplasmon energy as well as the energy of intralayer magnetoexciton is not affected by space symmetry. Three other collective magnetoplasmon modes as well as three magnetoexciton modes are determined by relations between the asymmetry parameter, tunnel parameter, and the difference in energies of intralayer and interlayer magnetoexcitons. The charge-density excitations in bilayer graphene at the filling-factor nu << 1 are considered. The presence of small asymmetry of graphene layers is taken into account. It is demonstarted that the magnetoplasmon energy depends on the bilayer ground state.