Evolution of dark energy reconstructed from the latest observations
  We reconstruct evolution of the dark energy (DE) density using a
nonparametric Bayesian approach from a combination of latest observational
data. We caution against parameterizing DE in terms of its equation of state as
it can be singular in modified gravity models, and using it introduces a bias
preventing negative effective DE densities. We find a $3.7\sigma$ preference
for an evolving effective DE density with interesting features. For example, it
oscillates around the $\Lambda$CDM prediction at $z\lesssim0.7$, and could be
negative at $z\gtrsim2.3$; dark energy can be pressure-less at multiple
redshifts, and a short period of cosmic deceleration is allowed at $0.1
\lesssim z\lesssim 0.2$. We perform the reconstruction for several choices of
the prior, as well as a evidence-weighted reconstruction. We find that some of
the dynamical features, such as the oscillatory behaviour of the DE density,
are supported by the Bayesian evidence, which is a first detection of a
dynamical DE with a positive Bayesian evidence. The evidence-weighted
reconstruction prefers a dynamical DE at a $(2.5\pm0.06)\sigma$ significance
level.
