  The electron-electron interactions effects on the shape of the Fermi surface
of doped graphene are investigated. The actual discrete nature of the lattice
is fully taken into account. A $\pi$-band tight-binding model, with
nearest-neighbor hopping integrals, is considered. We calculate the self-energy
corrections at zero temperature. Long and short range Coulomb interactions are
included. The exchange self-energy corrections for graphene preserve the
trigonal warping of the Fermi surface topology, although rounding the
triangular shape. The band velocity is renormalized to higher value.
Corrections induced by a local Coulomb interaction, calculated by second order
perturbation theory, do deform anisotropically the Fermi surface shape. Results
are compared to experimental observations and to other theoretical results.
