  Observational manifestations of accelerated expansion of the universe, in
particular, recent data for Type Ia supernovae, baryon acoustic oscillations,
for the Hubble parameter $H(z)$ and cosmic microwave background constraints are
described with different cosmological models. We compare the $\Lambda$CDM, the
models with generalized and modified Chaplygin gas and the model with quadratic
equation of state. For these models we estimate optimal model parameters and
their permissible errors with different approaches to calculation of sound
horizon scale $r_s(z_d)$. Among the considered models the best value of
$\chi^2$ is achieved for the model with quadratic equation of state, but it has
2 additional parameters in comparison with the $\Lambda$CDM and therefore is
not favored by the Akaike information criterion.

General Relativity and Quantum Cosmology