Analysis the neutral triplet collective mode in honeycomb lattice:   without one-cone approximation
  In this research has been studied the possibility of existence the neutral triplet collective mode in undoped graphene and graphite without one-cone approximation. This work tries to study this collective mode from different points of view. It also studies the effects of on-site Hubbard interaction on neutral collective mode in honeycomb lattice via two representations (sub-lattice and eigenvector). The effective long rang interaction in honeycomb lattice has been introduced for studying the spin collective mode. This work shows that short and effective long range interactions are not responsible for the formation of neutral triplet collective mode in graphene without {\it one-cone} approximation. 
M. Ebrahimkhas
cond-mat.str-el