The Cosmology of the Early and Late Universe

诺丁汉大学的粒子宇宙学和引力小组旨在了解宇宙中的基本粒子和力。我们通过研究支撑我们对物理学的理解的基本理论，也通过模拟我们所知道的物理学的行为，以及为解决基本的宇宙奥秘而提出的物理学，这样就可以将其与实验数据和宇宙观测进行比较。在我们生活的宇宙中，遥远的星系正在相互加速，但原因不可能是其中存在的普通物质，因为宇宙应该在引力对其所含物质的吸引力下减速。我们把导致这种加速的东西称为暗能量（DE），而最主要的候选者是宇宙常数（CC）。今天不可能有太多的暗物质，因为如果有的话，它会导致星系现在分崩离析，然而大多数量子理论预测的暗物质太多了。我们正在努力解决这种不平衡，并提出了一个解决CC被取消的问题的方案，有效地消除了它。我们打算发展我们对模型的理解，并询问是否可以在我们宇宙的粒子理论模型中发现它的存在，以及我们是否可以在致密物体中看到它的直接证据。我们也将致力于其他DE模型。在其中一个被称为Quintessence的课程中，我们将确定它是否存在于基础理论中，在另一个课程中，驱动加速度的力在高密度区域被屏蔽，比如在地球上，我们已经建立了一些特征，使我们能够在实验室和银河系尺度上对它们进行测试。另一种观点是，在大尺度上修改爱因斯坦的广义相对论（GR），而我们正在研究这样的模型。我们将在宇宙尺度上对它们进行测试，并观察它们如何影响中子星等大质量物体的形成。我们还将限制暗物质的模型，暗物质是宇宙中保持星系在一起的关键成分。我们还没有发现DM到底是什么，我们的目标之一是帮助发现将我们的星系结合在一起的神秘粒子。我们将研究在早期宇宙中形成的原始黑洞（PBH）的可能性，也许是一种叫做轴子的极轻粒子，或者可能是另一种叫做畴壁的粒子，在早期宇宙中形成。许多人认为，早期的宇宙在短暂的时间内经历了一个几乎呈指数级膨胀的阶段，即暴胀。我们将研究暴胀模型，以确定是否可以在弦理论中找到成功的模型。诺丁汉大学最近出现了一个新领域那就是通过模拟实验在实验室里测试重力理论的可能性。尽管它们的能量尺度与早期宇宙完全不同，但它们的方程相似，因此我们希望通过做这样的实验，我们可以模拟早期宇宙的效应，甚至利用实验来预测那些最早的时刻。黑洞和中子星周围的引力最强。我们将利用这一特性来测试修正的引力理论，并寻找引力的新特征——比如从黑洞中长出的标量场毛发！我们将使用涉及量子理论的数值模拟来演示黑洞形成后是如何通过发射霍金辐射而蒸发的。我们正在开发宇宙学模型，使我们能够谈论宇宙中最早的时刻，引力和量子力学的作用是至关重要的，并打算开发方法来约束和测试这些模型与天文数据，如在与大爆炸相关的热辐射中看到的波动。

The Particle Cosmology and Gravity groups at Nottingham aim to understand the fundamental particles and forces in our universe. We do this by working on the fundamental theoretical underpinning of our understanding of physics, and also by modelling the behaviour of the physics we know, and the physics proposed to solve fundamental cosmological mysteries, so that this can be compared with experimental data and cosmological observations.We live in a Universe in which distant galaxies are accelerating apart from one another, but the cause for this cannot be the ordinary matter present in it as the universe should be slowing down due to the attractive pull of gravity on the matter it contains. We call whatever is causing this acceleration dark energy (DE) and the leading candidate is the Cosmological Constant (CC). There can't be much of it around today because if there was, it would have caused galaxies to blow apart by now, yet most quantum theories predict far too much of it. We are trying to resolve this imbalance and have proposed a solution to the problem in which the CC is cancelled, effectively removing it. We intend to develop our understanding of the model and ask both whether it can be found to exist in particle theory models of our Universe and whether we can see direct evidence of it in compact objects. We will also be working on other DE models. In one of them known as Quintessence we will establish whether it exists in fundamental theory, and in another class where the force driving the acceleration is screened from view in regions of high density such as here on Earth, we have established a number of features they have that would allow us to test for them in the laboratory and on galactic scales. An alternative point of view to DE driving the acceleration of our universe, is to modify Einstein's General Theory of Relativity (GR) on large scales, and we work on such models. We will be testing them, both on cosmological scales and by seeing how they affect the formation of massive objects like neutron stars. We will also constrain models of Dark Matter, the key component of the universe which keeps galaxies together. We have yet to find out what DM really is, and one of our aims is to help uncover the mysterious particle that is binding our galaxy together. We will be working on the possibility that there may be primordial black holes (PBH) formed in the early universe, maybe an extremely light particle called the axion, or possibly another type of particle known as a domain wall formed in the early universe. Many people think the early Universe underwent a phase of almost exponential expansion for a brief period of time, known as Inflation. We will work on models of inflation to establish whether or not successful models can be found in string theory. A new area which has emerged here at Nottingham recently is the possibility of testing theories of gravity in the laboratory by creating analogue experiments. Although at a completely different energy scale to the early universe, they enjoy similar equations, hence the hope that by doing such experiments we can mimic early universe effects and even use the experiments to make predictions about those earliest moments. Gravity is at its strongest around Black holes and neutron stars. We will make use of this feature both to test for modified gravity theories and to look for new signatures of gravity - such as scalar field hair growing from the BHs! We will use numerical simulations involving quantum theory to demonstrate how black holes actually evaporate by emitting Hawking radiation once they have formed. We are developing models of cosmology that allow us to talk about the earliest moments in the universe, where the role of Gravity and Quantum Mechanics are vital, and intend to develop methods to constrain and test these models with astronomical data such as the fluctuations seen in the thermal radiation associated with the Big Bang.