  An exact analytical solution of the nonlinear boson diffusion equation (NBDE)
is presented. It accounts for the time evolution towards the Bose-Einstein
equilibrium distribution through inelastic and elastic collisions in case of
constant transport coefficients. As a currently interesting application, gluon
scattering in relativistic heavy-ion collisions is investigated. An estimate of
time-dependent gluon-condensate formation in overoccupied systems through
number-conserving elastic scatterings in Pb-Pb collisions at relativistic
energies is given.
