  In this paper we prove nonexistence of stationary weak solutions to the
Euler-Poisson equations and the Navier-Stokes-Poisson equations in $\Bbb R^N$,
$N\geq 2$, under suitable assumptions of integrability for the density,
velocity and the potential of the force field. For the time dependent
Euler-Poisson equations we prove nonexistence result assuming additionally
temporal asymptotic behavior near infinity of the second moment of density. For
a class of time dependent Navier-Stokes-Poisson equations this asymptotic
behavior of the density can be proved if we assume the standard energy
inequality, and therefore the nonexistence of global weak solution follows from
more plausible assumption in this case.
