Constraints and cosmography of $\Lambda$CDM in presence of viscosity

Understand

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 $0.01<z<2.36$.