Dynamic equilibrium models and capital accumulation process in economics

In my thesis, I examined a total of seven economic growth models, five of which are closed economies and two open economies. Based on the Solow Model, one of the models I examined, I examined the capital accumulation process of a medium-sized country under the Solow Model structure. I used differential equations and optimal control theory as a method in the study of economic growth models.\\ I created an Open Economy Breakthrough Solow Model by adding an external savings function to the Solow Model. In this model, as in the Solow Model, the growth rate of long-term capital per capita and income per capita is zero. Three scenarios emerge that determine the per capita capital value that the country will reach, depending on the value taken by the threshold variable of capital per capita, which equates only the foreign interest rate with the marginal return of domestic capital.\\ In these three scenarios, three different steady-state equilibrium capital value per capita are obtained. The steady state point of the model country is determined by the threshold capital value per capita. When the threshold value of capital per capita changes, the steady-state equilibrium changes as well.