The Logotropic Dark Fluid: Observational and Thermodynamic Constraints
  We have considered a spatially flat, homogeneous and isotropic FLRW Universe
filled with a single fluid, known as logotropic dark fluid (LDF), whose
pressure evolves through a logarithmic equation of state. We use the recent
Pantheon SNIa and cosmic chronometer datasets to constrain the parameters of
this model, the present fraction of dark matter $\Omega_{m0}$ and the Hubble
constant $H_0$. We find that the mean values of these parameters are
$\Omega_{m0}=0.288\pm 0.012$ and $H_{0}=69.652\pm 1.698~{\rm km/s/Mpc}$ at the
$1\sigma$ CL. We also find that the LDF model shows a smooth transition from
the deceleration phase to acceleration phase of the universe in the recent
past. We notice that the redshift of this transition $z_{t}=0.706\pm 0.048$
($1\sigma$ error) and is well consistent with the present observations.
Interestingly, we find that the Universe will settle down to a $\Lambda$CDM
model in future and there will not be any future singularity in the LDF model.
Furthermore, we notice that there is no significant difference between the LDF
and $\Lambda$CDM models at the present epoch, but the difference (at the
percent level) between these models is found as the redshift increases. We have
also studied the generalized second law of thermodynamics at the dynamical
apparent horizon for the LDF model with the Bekenstein and Viaggiu entropies.
