New observational constraints on $f(R)$ gravity from cosmic chronometers
  We use the recently released cosmic chronometer data and the latest measured
value of the local Hubble parameter, combined with the latest joint light
curves of Supernovae Type Ia, and Baryon Acoustic Oscillation distance
measurements, in order to impose constraints on the viable and most used $f(R)$
gravity models. We consider four $f(R)$ models, namely the Hu-Sawicki, the
Starobinsky, the Tsujikawa, and the exponential one, and we parametrize them
introducing a distortion parameter $b$ that quantifies the deviation from
$\Lambda$CDM cosmology. Our analysis reveals that a small but non-zero
deviation from $\Lambda$CDM cosmology is slightly favored, with the
corresponding fittings exhibiting very efficient $AIC$ and $BIC$ Information
Criteria values. Clearly, $f(R)$ gravity is consistent with observations, and
it can serve as a candidate for modified gravity.
