Observational constraints on generalized Proca theories
  In a model of the late-time cosmic acceleration within the framework of
generalized Proca theories, there exists a de Sitter attractor preceded by the
dark energy equation of state $w_{\rm DE}=-1-s$, where $s$ is a positive
constant. We run the Markov-Chain-Monte-Carlo code to confront the model with
the observational data of Cosmic Microwave Background (CMB), baryon acoustic
oscillations, supernovae type Ia, and local measurements of the Hubble
expansion rate for the background cosmological solutions and obtain the bound
$s=0.254^{{}+ 0.118}_{{}-0.097}$ at 95% confidence level (CL). Existence of the
additional parameter $s$ to those in the $\Lambda$-Cold-Dark-Matter
($\Lambda$CDM) model allows to reduce tensions of the Hubble constant $H_0$
between the CMB and the low-redshift measurements. Including the cosmic growth
data of redshift-space distortions in the galaxy power spectrum and taking into
account no-ghost and stability conditions of cosmological perturbations, we
find that the bound on $s$ is shifted to $s=0.16^{+0.08}_{-0.08}$ (95 % CL) and
hence the model with $s>0$ is still favored over the $\Lambda$CDM model. Apart
from the quantities $s, H_0$ and the today's matter density parameter
$\Omega_{m0}$, the constraints on other model parameters associated with
perturbations are less stringent, reflecting the fact that there are different
sets of parameters that give rise to a similar cosmic expansion and growth
history.
