Solutions of evolution equations with the semigroup theory

In the first part of this thesis, the physical meanings of Lamé equation, delayed equations and equations containing logarithmic source terms are given. In addition, the historical process of delayed differential equations is mentioned. Some emerging models of delayed differential equations are also given. In the second part, the purpose of the thesis is stated and the areas where the equations with delayed terms are used in general are given. These fields have emerged in fields such as optics, nuclear physics, quantum mechanics, and geophysics in general. Then, basic studies on problems with delayed terms are given. Here, firstly, the problem that Kafini worked on in 2021 is given, and then Taouaf et al.'s work in 2018 is given. The third part consists of five parts. Firstly, the definition of Lebesgue space is given in the first part. In the second part, the definition of Sobolev space and the Sobolev Embedding theorem are given. In the third part, the Young, Hölder, Sobolev and Sobolev-Poincare inequalities required throughout the thesis are included. In the fourth part, Fourier Series and Parseval Identity are expressed. In the fifth part, there are definitions, lemmas and theorems related to the Semigroup Method. The fourth chapter is the main part of the thesis and consists of three subsections related to the Logarithmic Source Term Lamé System. In the first part, the goodness of our equation with logarithmic source term, which includes a delayed term, is studied. Here, first of all, the existence and uniqueness of the problem is proved by semigroup method by arranging the delayed equation with the help of a transformation. In the second part, its global presence is shown with the potential depth method. In this section, the proof of global existence is found with the help of potential depth method. In the third chapter, the exponential reduction of the equation is studied. The exponential decrease studied in this chapter has been proved by the theorems and lemmas given in the thesis. In the fifth chapter, the conclusion and suggestions of the thesis are given.