Study of multiple axion cosmologies

对类轴子粒子的研究为理解粒子物理学和宇宙结构中的一系列物理现象提供了一种有趣而有前途的方法。从QCD物理的早期开始，人们就发现QCD的作用被允许包含一个违反CP的项。通过Peccei和Quinn的工作，假设打破新引入的U(1)对称性将产生一个被称为轴子的自旋为零的轻粒子。很快就变得明显的是，理论表明在大爆炸期间可能有大量的轴子被创造出来。如果轴子表现出某些性质，防止其他衰变模式，宇宙将由原始轴子构成。因此，轴子似乎可以为观测到的物理宇宙的暗物质密度提供解释。目前关于类轴子粒子的宇宙学和天体物理学的观点为膨胀和当今膨胀宇宙的结构形成等领域提供了一个非常重要的框架。各种弦理论的一般预测是存在许多类似轴子的粒子。在弦理论的背景下，轴子似乎为暗能量/暗物质的演化提供了有希望的候选者，并通过经典理论解释了宇宙常数。因此，重要的是应该使用宇宙学观测，以便对这些场可能具有的性质施加限制。了解这些标量场相对于高阶模型的演化，以便重现我们今天观察到的宇宙的宇宙学观测，将成为这个项目的基础，通过研究多个轴子宇宙学。

The study of axion-like particles provides an interesting and promising approach to understanding a range of physical phenomena in particle physics and the structure of the universe. Since the early days of QCD physics, it was found that that the action of QCD was permitted to contain a CP-violating term. Through the work of Peccei and Quinn it was postulated that breaking a newly introduced U(1) symmetry would give rise to a light spin zero particle known as the axion. It soon became apparent that theories suggested axions could have been created in abundance during the Big Bang. If axions presented certain properties, preventing other decay modes, the universe would be constructed with primordial axions. Axions could therefore plausibly provide an explanation to the observed dark matter density of the physical universe. The current view on the cosmology and astrophysics of axion-like particles provides a very important framework for areas such as inflation and the structural formation of the present-day expanding Universe. A generic prediction of various string theories is the presence of many axion like particles. In the context of string theory, axions appear to provide promising candidates for dark energy/dark matter evolution and explaining the cosmological constant via quintessence. Therefore, it is important that cosmological observations should be used in order to place constraints on the properties these fields might have. Understanding the evolution of these scalar fields in respect to higher order models, in order to reproduce the cosmological observations of the universe we observe today, will serve as a foundation to this project by investigating multiple axion cosmologies.