Fermi point in graphene as a monopole in momentum space
  We consider the effective field theory of graphene monolayer with the Coulomb interaction between fermions taken into account. The gauge field in momentum space is introduced. The position of the Fermi point coincides with the position of the corresponding monopole. The procedure of extracting such monopoles during lattice simulations is suggested. 
M .A. Zubkov
hep-lat cond-mat.str-el