Evolution of gaseous disk viscosity driven by supernova explosion in
  star-forming galaxies at high redshift
  Motivated by Genzel et al.'s observations of high-redshift star-forming
galaxies, containing clumpy and turbulent rings or disks, we build a set of
equations describing the dynamical evolution of gaseous disks with inclusion of
star formation and its feedback. Transport of angular momentum is due to
"turbulent" viscosity induced by supernova explosions in the star formation
region. Analytical solutions of the equations are found for the initial cases
of a gaseous ring and the integrated form for a gaseous disk, respectively. For
a ring with enough low viscosity, it evolves in a slow processes of gaseous
diffusion and star formation near the initial radius. For a high viscosity, the
ring rapidly diffuses in the early phase. The diffusion drives the ring into a
region with a low viscosity and start the second phase undergoing pile-up of
gas at a radius following the decreased viscosity torque. The third is a
sharply deceasing phase because of star formation consumption of gas and
efficient transportation of gas inward forming a stellar disk. We apply the
model to two $z\sim 2$ galaxies BX 482 and BzK 6004, and find that they are
undergoing a decline in their star formation activity.
