Constraints and cosmography of $\Lambda$CDM in presence of viscosity
  In this work, we study two scenarios of the Universe filled by a perfect
fluid following the traditional dark energy and a viscous fluid as dark matter.
In this sense, we explore the simplest case for the viscosity in the Eckart
formalism, a constant, and then, a polynomial function of the redshift. We
constrain the phase-space of the model parameters by performing a Bayesian
analysis based on Markov Chain Monte Carlo method and using the latest data of
the Hubble parameter (OHD), Type Ia Supernovae (SNIa) and Strong Lensing
Systems. The first two samples cover the region $0.01<z<2.36$. Based on AIC, we
find equally support of these viscous models over Lambda-Cold Dark Matter
(LCDM) taking into account OHD or SNIa. On the other hand, we reconstruct the
cosmographic parameters ($q,j,s,l$) and find good agreement to LCDM within up
to $3\sigma$ CL. Additionally, we find that the cosmographic parameters and the
acceleration-deceleration transition are sensible to the parameters related to
the viscosity coefficient, making of the viscosity an interesting physical
mechanism to modified them.
