Exactly solvable wormhole and cosmological models with a barotropic   equation of state
  An exact solution of the Einstein field equations given the barotropic equation of state $p=\omega\rho$ yields two possible models: (1) if $\omega <-1$, we obtain the most general possible anisotropic model for wormholes supported by phantom energy and (2) if $\omega >0$, we obtain a model for galactic rotation curves. Here the equation of state represents a perfect fluid which may include dark matter. These results illustrate the power and usefulness of exact solutions. 
Peter K.F. Kuhfittig
gr-qc