Almost paracontact mani̇folds

In this thesis, almost paracontact manifolds are studied. After giving basic concepts on almost paracontact manifolds, the classification of these manifolds is examined. Almost paracontact metric manifolds were classified according to the Levi-Civita covariant derivatives of their fundamental two-forms. In addition, the classes of normal, paracontact, para-Sasakian and quasi-para-Sasakian manifolds are considered. Furthermore the existence of eta-Einstein structures on 5 dimensional nilpotent Lie algebras are studied. Also examples of almost paracontact metric structures on 5 dimensional nilpotent Lie algebras are given and their classes are determined. Finally the existence of quasi-para-Sasakian structures on 5 dimensional nilpotent Lie algebras is analysed.