On the dark contents of the Universe: A Euclid survey approach
  In this work we study the consequences of allowing non pressureless dark matter when determining dark energy constraints. We show that present-day dark energy constraints from low-redshift probes are extremely degraded when allowing this dark matter variation. However, adding the cosmic microwave background (CMB) we can recover the $w_{DM} = 0$ case constraints. We also show that with the future Euclid redshift survey we expect to largely improve these constraints; but, without the complementary information of the CMB, there is still a strong degeneracy between dark energy and dark matter equation of state parameters. 
Isaac Tutusaus, Brahim Lamine and Alain Blanchard
astro-ph.CO