  It is stated that holonomy corrections in loop quantum cosmology introduce a
modification in Friedmann's equation which prevent the big rip singularity.
Recently in \cite{h12} it has been proved that this modified Friedmann equation
is obtained in an inconsistent way, what means that the results deduced from
it, in particular the big rip singularity avoidance, are not justified. The
problem is that holonomy corrections modify the gravitational part of the
Hamiltonian of the system leading, after Legendre's transformation, to a non
covariant Lagrangian which is in contradiction with one of the main principles
of General Relativity. A more consistent way to deal with the big rip
singularity avoidance is to disregard modification in the gravitational part of
the Hamiltonian, and only consider inverse volume effects \cite{bo02a}. In this
case we will see that, not like the big bang singularity, the big rip
singularity survives in loop quantum cosmology. Another way to deal with the
big rip avoidance is to take into account geometric quantum effects given by
the the Wheeler-De Witt equation. In that case, even though the wave packets
spread, the expectation values satisfy the same equations as their classical
analogues. Then, following the viewpoint adopted in loop quantum cosmology, one
can conclude that the big rip singularity survives when one takes into account
these quantum effects. However, the spreading of the wave packets prevents the
recover of the semiclassical time, and thus, one might conclude that the
classical evolution of the universe come to and end before the big rip is
reached. This is not conclusive because. as we will see, it always exists other
external times that allows us to define the classical and quantum evolution of
the universe up to the big rip singularity.
