الخلاصة:
In this thesis we have suggested two cosmological models.in the first one we
have studied the dynamical behaviors and stability properties of a flat space
FRW universe filled with pressureless dark matter and viscous dark energy in
the context of standard classical and loop quantum cosmology. Assuming that
the dark energy has a constant bulk viscosity, it is found that the bulk viscosity
effects influence only the quintessence model case leading to the existence of
a viscous late time attractor solution of de-Sitter type, whereas, the quantum
geometry effects influence the phantom model case where the big rip
singularity is removed. Moreover, compared with the more recent data, our
results of the Hubble parameter as a function of the redshift are in a good
agreement. However, in the second model we have studied the dynamical
behaviors and stability properties of a flat space FRW universe filled with
pressureless dark matter and viscous dark energy in the context of loop
quantum cosmology. Assuming that the dark energy has bulk viscosity in the
general form, we have found there exists under some appropriate parameters
a stable late time viscous dark energy dominated solution of de Sitter type. the
problem of future singularity (big rip) will never occur in this scenario.
