Dynamical dark energy in light of the latest observations
  A flat Friedman-Roberson-Walker universe dominated by a cosmological constant
($\Lambda$) and cold dark matter (CDM) has been the working model preferred by
cosmologists since the discovery of cosmic acceleration. However, tensions of
various degrees of significance are known to be present among existing datasets
within the $\Lambda$CDM framework. In particular, the Lyman-$\alpha$ forest
measurement of the Baryon Acoustic Oscillations (BAO) by the Baryon Oscillation
Spectroscopic Survey (BOSS) prefers a smaller value of the matter density
fraction $\Omega_{\rm M}$ compared to the value preferred by cosmic microwave
background (CMB). Also, the recently measured value of the Hubble constant,
$H_0=73.24\pm1.74 \ {\rm km}\ {\rm s}^{-1} \ {\rm Mpc}^{-1}$, is $3.4\sigma$
higher than $66.93\pm0.62 \ {\rm km}\ {\rm s}^{-1} \ {\rm Mpc}^{-1}$ inferred
from the Planck CMB data. In this work, we investigate if these tensions can be
interpreted as evidence for a non-constant dynamical dark energy (DE). Using
the Kullback-Leibler (KL) divergence to quantify the tension between datasets,
we find that the tensions are relieved by an evolving DE, with the dynamical DE
model preferred at a $3.5\sigma$ significance level based on the improvement in
the fit alone. While, at present, the Bayesian evidence for the dynamical DE is
insufficient to favour it over $\Lambda$CDM, we show that, if the current best
fit DE happened to be the true model, it would be decisively detected by the
upcoming DESI survey.
