本文先简要介绍了重整化方法，之后我们概述了，我们提出的底层理论的基本逻辑，并简要介绍了分形几何的数学基础。在说明了我们所说的底层理论中最核心的部分，即对发散积分的处理方法后，会着重讨论Casimir效应与真空能问题，给出了底层理论所提出的实验预言并和现在量子场论结果进行对比，在之后说明这个理论是如何在可重整化理论中生效的。最后简要的讨论在不可重整理论中，主要是引力理论中底层理论的行为。

 本论文共分六章，第一章绪论；第二章为重整化方法；第三章是分形与底层理论；第四章是Casimir效应与宇宙学常数；第五章是底层理论的可行性；第六章是总结和展望。第一章绪论概述了本文的主要动机；第二章、第三章第二节以及第四章的第一和第三小节介绍的是现有的理论和前人的工作，第三章第一、三、四、五小节，第四章第二和第四小节以及第五章是作者本人的工作;第六章简述了作者现有的工作结果以及进一步工作的方向。

In this thesis, we first briefly introduce the renormalization method, and then we outline the basic logic of the underlying theory put forward by us and  the mathematical basis of fractal geometry. Then the core part of what we call the underlying theory, that is, the method of dealing with divergent integrals, will be explained. We will apply the method to the issue of Casimir effect and vacuum energy, and give the experimental predictions proposed by the underlying theory and the conventional quantum field theory. The results are compared, and it is explained  how the underlying theory works in renormalizable theories. Finally, we will discuss the behavior of the underlying theory in non-renormalizable theory.

This thesis is divided into six chapters. The first chapter is an introduction; In the second chapter the renormalization method in field theories is introduced; In the third chapter the fractal and the underlying theories are discussed; In the fourth chapter the Casimir effect and cosmological constant are discussed by using the underlying theory ; In the fifth chapter the feasibility of the underlying theory is discussed ; Chapter 6 is a summary and outlook. The main motivation of this thesis is outlined in the first chapter . The second and fourth chapters are devoted to introduce existing theories and previous work, and the third and fifth chapters are the author's own work. The author's results and the direction of further works are briefly discussed in Chapter six.