Operator ideals defined by some sequence spaces

In this work, operator ideals defined by some sequence spaces are studied. This thesis consists of four chapter and the original results of the thesis are given in the third and the fourth chapter. Firstly literature review and the basic concepts with definitions used in the thesis are given. Then the class of Stolz p-type mappings defined by Iseki is generalized to the class of generalized Stolz mappings. It is also shown that this class is an operator ideal and a quasi-Banach operator ideal by a quasi-norm defined on this class. Then classes defined by using other examples of the s-number sequences and various properties provided by these classes are examined. Later on a generalized class of Stolz transformations is defined by using generalized approximation numbers. Also a new operator ideal is defined by using symmetric norming function and generalized Stolz transformations. Subsequently various operator ideals are defined on the block sequence spaces. The class of $s$-type l_p(E) operators, the class of operators which are generated by the symmetric norming function with s-type l_p(E) operators and the class of s-type Z(u,v;l_p (E)) operators are given respectively. It is also shown that all of these new classes are operator ideals and quasi-Banach operator ideals by a quasi-norm defined on relevant classes. Then classes defined by using the other examples of s- number sequences and various properties provided by these classes are examined. Finally some equivalent quasi-norms on these operator ideals are given.