.الدراسة الديناميكية لنموذج الطاقة المظلمة اللزجة في الكوسمولوجيا الكلاسيكية و الجاذبية الكوانتية الحلقية

Abstract

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.