  In recent years, control of group velocity of light has attracted enormous
interest. One of the main challenges is to realize an absorption-free fast or
slow light propagation. Here, we study dispersion and absorption properties of
a weak probe field in a Landau-quantized graphene and report a gain-assisted
superluminal light propagation. Moreover, an attempt is made to develop an
analytical expression and necessary parameters for switching the group velocity
of the probe field from subluminal to superluminal. It's worth mentioning that
large dephasing rate in graphene offers feasibility of superluminal propagation
of ultrashort light pulses. Additionally, dynamical behavior of dispersion and
absorption of a weak probe field in a closed-type graphene system is
investigated, and it is found that the absorption and dispersion can be
dramatically affected by both the relative phase of applied fields and the Rabi
frequencies in such a way that a large transient gain can be achieved and a
transient absorption can be completely eliminated.
