In this thesis, we mainly investigated GPP- ring and several special modules and their homological dimensions.We divide the thesis into four chapters. Chapter 1 is introduction.we introduce the importance of homological theory in Algebras, and the close relations with other algebraic branchs. We introduce the work in this thesis.In chapter 2. we discuss some properties of GPP- ring and the relations between GPP- ring and - regular ring.In chapter 3, we discuss n - flat modules and n - FP - injective modules, we define n - flat dimension and n - FP - injective dimension, we consider n - flat modules and n - FP - injective modules in commutative n- coherent rings, their properties are similar to flat and injectivc modules in commutative coherent rings.In chapter 4, we define the projective dimension of flat modules, use it to characterize many rings, and the relations between cotorsion modules and the projective dimension of flat modules are also given. |