Late time cosmic acceleration from natural infrared cutoff?
  In this paper, inspired by the ultraviolet deformation of the
Friedmann-Lema\^{\i}tre-Robertson-Walker geometry in loop quantum cosmology, we
formulate an infrared-modified cosmological model. We obtain the associated
deformed Friedmann and Raychaudhuri equations and we show that the late time
cosmic acceleration can be addressed by the infrared corrections. As a
particular example, we applied the setup to the case of matter dominated
universe. This model has the same number of parameters as $\Lambda$CDM, but a
dynamical dark energy generates in the matter dominated era at the late time.
According to our model, as the universe expands, the energy density of the cold
dark matter dilutes and when the Hubble parameter approaches to its minimum,
the infrared effects dominate such that the effective equation of state
parameter smoothly changes from $w_{_{\rm eff}}=0$ to $w_{_{\rm eff}}=-2$.
Interestingly and nontrivially, the unstable de Sitter phase with $w_{_{\rm
eff}}=-1$ is corresponding to $\Omega_m=\Omega_d =0.5$ and the universe crosses
the phantom divide from the quintessence phase with $w_{_{\rm eff}}>-1$ and
$\Omega_m> \Omega_d$ to the phantom phase with $w_{_{\rm eff}}<-1$ and $
\Omega_m<\Omega_d$ which shows that the model is observationally viable. The
results show that the universe finally ends up in a big rip singularity for a
finite time proportional to the inverse of the minimum of the Hubble parameter.
Moreover, we consider the dynamical stability of the model and we show that the
universe starts from the matter dominated era at the past attractor with
$w_{_{\rm eff}}=0$ and ends up in a future attractor at the big rip with
$w_{_{\rm eff}}=-2$.
