Charge density excitations in bilayer graphene in high magnetic field

The charge-density excitations in bilayer graphene at the filling-factor $\nu\ll1$ at small momenta are considered in the frame of the Hartree-Fock approximation. The presence of small asymmetry of graphene layers is included. The dependence of the magnetoplasmon energy on the bilayer ground state is shown. The energy splitting proportional to $\sqrt H$ for the symmetric case with half-filled zero-energy levels is found both for bilayer and monolayer graphene.