Speeding up the universe using dust with pressure
  We revise the cosmological standard model presuming that matter, i.e. baryons
and cold dark matter, exhibits a non-vanishing pressure mimicking the
cosmological constant effects. In particular, we propose a scalar field
Lagrangian $\mathcal L_1$ for matter with the introduction of a Lagrange
multiplier as constraint. We also add a symmetry breaking effective potential
accounting for the classical cosmological constant problem, by adding a second
Lagrangian $\mathcal{L}_2$. Investigating the Noether current due to the shift
symmetry on the scalar field, $\varphi\rightarrow\varphi+c^0$, we show that
$\mathcal{L}_1$ turns out to be independent from the scalar field $\varphi$.
Further we find that a positive Helmotz free-energy naturally leads to a
negative pressure without introducing by hand any dark energy term. To face out
the fine-tuning problem, we investigate two phases: before and after transition
due to the symmetry breaking. We propose that during transition dark matter
cancels out the quantum field vacuum energy effects. This process leads to a
negative and constant pressure whose magnitude is determined by baryons only.
The numerical bounds over the pressure and matter densities are in agreement
with current observations, alleviating the coincidence problem. Finally
assuming a thermal equilibrium between the bath and our effective fluid, we
estimate the mass of the dark matter candidate. Our numerical outcomes seem to
be compatible with recent predictions on WIMP masses, for fixed spin and
temperature. In particular, we predict possible candidates whose masses span in
the range $0.5-1.7$ TeV.
