Observational constraints of $f(Q)$ gravity
  In this work, we consider an extension of symmetric teleparallel gravity,
namely, $f(Q)$ gravity, where the fundamental block to describe spacetime is
the nonmetricity, $Q$. Within this formulation of gravitation, we perform an
observational analysis of several modified $f(Q)$ models using the redshift
approach, where the $f(Q)$ Lagrangian is reformulated as an explicit function
of the redshift, $f(z)$. Various different polynomial parameterizations of
$f(z)$ are proposed, including new terms which would allow for deviations from
the $\Lambda$CDM model. Given a variety of observational probes, such as the
expansion rate data from early-type galaxies, Type Ia Supernovae, Quasars,
Gamma Ray Bursts, Baryon Acoustic Oscillations data and Cosmic Microwave
Background distance priors, we have checked the validity of these models at the
background level in order to verify if this new formalism provides us with
plausible alternative models to explain the late time acceleration of the
universe. Indeed, this novel approach provides a different perspective on the
formulation of observationally reliable alternative models of gravity.
