  We investigate the creation of massless quasiparticle pairs from the vacuum
state in graphene by the space homogeneous time-dependent electric field. For
this purpose the formalism of (2+1)-dimensional quantum electrodynamics is
applied to the case of a nonstationary background with arbitrary time
dependence allowing the S-matrix formulation of the problem. The number of
created pairs per unit graphene area is expressed via the asymptotic solution
at $t\to\infty$ of the second-order differential equation of an oscillator type
with complex frequency satisfying some initial conditions at $t\to-\infty$. The
obtained results are applied to the electric field with specific dependence on
time admitting the exact solution of Dirac equation. The number of created
pairs per unit area is calculated analytically in a wide variety of different
regimes depending on the parameters of electric field. The investigated earlier
case of static electric field is reproduced as a particular case of our
formalism. It is shown that the creation rate in a time-dependent field is
often larger than in a static field.
