Testing a dissipative kinetic k-essence model
  In this work, we present a study of a purely kinetic k-essence model,
characterized basically by a parameter $\alpha$ in presence of a bulk
dissipative term, whose relationship between viscous pressure $\Pi$ and energy
density $\rho$ of the background follows a polytropic type law $\Pi \propto
\rho^{\lambda+1/2}$, where $\lambda$, in principle, is a parameter without
restrictions. Analytical solutions for the energy density of the k-essence
field are found in two specific cases: $\lambda=1/2$ and
$\lambda=(1-\alpha)/2\alpha$, and then we show that these solutions posses the
same functional form than the non-viscous counterpart. Finally, both approach
are contrasted with observational data from type Ia supernova, and the most
recent Hubble parameter measurements, and therefore, the best values for the
parameters of the theory are founds.
