Inelastic scattering of Xray photons from electrons give them a wavelength shift, the Compton effect. The shift is inverse proportional with the mass of the electron. Now, if visible light scatters inelastic from electrons in graphene what will be the wavelength shift? The electrons in graphene 'behave' massless ... Can this be calculated with QED using the graphene Hamiltonian H = -vf.sigma.(p-eA/c)? Then we should calculate the perturbation up to second order? Thanks! Claude.