Analytical Blowup Solutions to the 3-dimensional Pressureless Navier-Stokes-Poisson Equations with Density-dependent Viscosity

We study the pressureless Navier--Stokes-Poisson equations of describing the evolution of the gaseous star in astrophysics. The isothermal blowup solutions of Yuen, to the Euler-Poisson equations in R2, can be extended to the pressureless Navier-Stokes-Poisson equations with density-dependent viscosity in R3. Besides some remarks, about the meaning of the blowup solutions and the applicability of such solutions to the the drift-diffusion model in semiconductors, are discussed in the end.