Current constraints on the dark energy equation of state

We combine complementary datasets from cosmic microwave back.-round (CMB) anisotropy measurements, high redshift supernovae (SNIa) observations and data from local cluster abundances and galaxy clustering (LSS) to constrain the dark energy equation of state parametrized by a constant pressure-to-density ratio w(Q). Under the assumption of flatness, we find w(Q)< -0.85 at 68% C.L., providing no significant evidence for quintessential behavior different from that of a cosmological constant. We then generalize our result to show that the constraints placed on a constant w(Q) can be safely extended to dynamical theories. We consider a variety of quintessential dynamical models based on inverse power law, exponential and oscillatory scaling potentials. We find that SNIa observations are "numbed" to dynamical shifts in the equation of state, making the prospect of reconstructing w(z) a challenging one indeed.