Orynbasarov D.2025-07-302025-07-302019Orynbasarov D / Conservative extension in various classes of complete theories models / 6M060100 - Department of Mathematics and Natural Sciences / 2019https://repository.sdu.edu.kz/handle/123456789/1833This thesis is devoted to the in-depth study of the Bektur Baizhanov's "conservative extension of models of weakly o-minimal theories" and the solution of the problem whether it is possible to determine through a conservative extension, nonlocally isolated type. I studied the concept of rational section quasi-rational section and irrational section, extension and elementary extension, orthogonality of types, basic properties of types. Notion of quasi-model (or Tarskii-Vaught type) and any types will be isolated or non-isolated and non-isolated type in turn divides by two kind. It's locally isolated (another word strictly definable) and non-locally isolated. Moreover any types will be definable and non-definable and any isolated type is definable. But is an non-isolated type definable? I was looking for the answer to that question and answered in this thesis. Using the concept of a control formula, I proved that a non-locally isolated type can be definable.enweakly o-minimal theoriesTarskii-Vaught typequantifiersThesis