▎ 摘　　要

The optical conductivity of graphene is studied in detail. It is shown how crossover from nonlinear to linear behaviour of the current density occurs when the frequency of the external electric field is increased. We also study electron-hole pair creation in bilayer graphene and show that its rate in a static electric field is determined by a power law as for single-layer graphene but with a different exponent. Subsequently, transport in carbon nanotubes is studied.