Collective excitations of graphene excitons being in the Bose-Einstein   condensate state
  Bose-Einstein condensation of the excitons in graphene is considered. We suggested the model spinor equation for neutral particles with short range interaction described the microscopic graphene excitons dynamic. Using this equation we derived quantum hydrodynamic equations for description of collective properties of excitons in graphene, particularly for the case when excitons being in the Bose-Einstein condensate (BEC) state. The dispersion of collective excitations in graphene excitons BEC is studied. We shown that frequency of collective excitations is proportional to the square root of the wave vector module: $\omega\sim \sqrt{k}$. 
P. A. Andreev
cond-mat.mes-hall cond-mat.quant-gas cond-mat.stat-mech quant-ph