Core theorems for double sequences

The present thesis consists of five chapters.In the first chapter, a brief history of the concepts of double sequences and core are given.In the second chapter, some basic definitions and theorems related to double sequences and core are expressed.The third, fourth and fifth chapters of this thesis involve the original results.In the third chapter, some definitions and theorems related to the core of single sequences are extended to the double sequences.In the fourth chapter, some properties and duals of the sets of Ces\`{a}ro Pringsheim, Ces\`{a}ro bounded Pringsheim and Ces\`{a}ro bounded and null Pringsheim convergent double sequences, denoted by $Ces_p$, $Ces_{bp}$ and $Ces_{bp0}$, respectively, are examined.In the fifth chapter, some matrix classes into Ces\`{a}ro double sequence spaces are characterized and the proofs of some theorems related to Ces\`{a}ro core of double sequences are given.