Cosmological Constraints on Higgs-Dilaton Inflation
  We test the viability of the Higgs-dilaton model (HDM) compared to the
evolving dark energy ($w_0 w_a$CDM) model, in which the cosmological constant
model $\Lambda$CDM is also nested, by using the latest cosmological data that
includes the cosmic microwave background temperature, polarization and lensing
data from the \textit{Planck} satellite (2015 data release), the BICEP and Keck
Array experiments, the Type Ia supernovae from the JLA catalog, the baryon
acoustic oscillations from CMASS, LOWZ and 6dF, the weak lensing data from the
CFHTLenS survey and the matter power Spectrum measurements from the SDSS (data
release 7). We find that the values of all cosmological parameters allowed by
the Higgs-dilaton inflation model are well within the \textit{Planck} satellite
(2015 data release) constraints. In particular, we have that $w_0 =
-1.0001^{+0.0072}_{-0.0074}$, $w_a = 0.00^{+0.15}_{-0.16}$, $n_s =
0.9693^{+0.0083}_{-0.0082}$, $\alpha_s = -0.001^{+0.013}_{-0.014}$ and
$r_{0.05} = 0.0025^{+0.0017}_{-0.0016}$ (95.5\%C.L.). We also place new
stringent constraints on the couplings of the Higgs-dilaton model and we find
that $\xi_{\chi} < 0.00328$ and $\xi_h / \sqrt{\lambda} =
59200^{+30000}_{-20000}$ (95.5\%C.L.). Furthermore, we report that the HDM is
at a slightly better footing than the $w_0 w_a$CDM model, as they both have
practically the same chi-square, i.e. $\Delta \chi^2 = \chi^2_{w_0
w_a\mathrm{CDM}}-\chi^2_{\mathrm{HDM}}=0.18$, with the HDM model having two
fewer parameters. Finally Bayesian evidence favors equally the two models, with
the HDM being preferred by the AIC and DIC information criteria.
