The clustering of dark energy
  A cosmological model with pressurelless matter and a fluid of negative pressure is studied. At perturbative level, fluctuations of both fluids are considered. It is shown that at least at very large scales, the fluid of negative pressure, which represents the dark energy content of the universe, clusters like the dust fluid. Numerical integration reveals that this behaviour may also occur at scales smaller than the Hubble radius. 
F.G. Alvarenga, J.C. Fabris, S.V.B. Gon\c{c}alves and G. Tadaiesky