The Cosmology of the Early and Late Universe

我们的宇宙正在加速，遥远的星系以不断增加的速度移动，但我们不知道这种加速的来源，将其称为暗能量（DE）。我们工作的一个关键目标是确定这种神秘物质的性质，包括它是否标志着爱因斯坦对最大尺度引力描述的崩溃。宇宙常数（CC）是最简单的DE候选者，但它必须驱动加速度的值至少比我们基于物质量子理论自然期望的值低60个数量级。正如泡利曾经观察到的那样，电子对CC的贡献应该导致一个宇宙的大小不大于地月距离！我们已经开发了两种方法来处理CC，并将分析它们的宇宙学。在这两种情况下，我们都考虑了爱因斯坦原始引力模型的受控偏差，使我们能够消除这些对CC的巨大贡献。除了这些模型，我们继续询问有关DE的性质，以及其他称为变色龙的新的长距离现象，开发新的方法来考虑它们对加速器中粒子的影响，以及对实验室真空室中冷原子的影响。暗物质（DM）是一种难以看到的虚幻物质，因为它不与电磁相互作用，但它完全主导了宇宙的物质含量，驱动着星系的动力学。目前，我们主要有两种方法来探测DM粒子：一种是在地下深处的直接探测实验中，粒子与重原子的原子核碰撞，原子核的反冲被灵敏的探测器拾取，另一种是通过间接测量衰变产物，例如由于DM粒子在太阳中湮灭而产生的非常高能量的伽马射线。到目前为止，这两种方法在某种程度上相互排斥，使用不同的方法进行分析。在本提案中，我们打算开发技术，以便对直接和间接检测数据进行一致的比较，从而将这些社区聚集在一起，增加检测的机会。早期宇宙很可能由两种或两种以上的弦组成，一种是基本弦，它的振荡模式为我们提供了今天所看到的粒子，另一种是在相变过程中形成的宇宙弦。这两种弦都会随着宇宙的膨胀而演化，我们可以模拟它们的演化。因为它们的质量非常大（例如，一公里的宇宙弦将有月球的质量），它们扰动了它们运动的时空，导致弦附近区域的光的温度发生扭曲。我们在由大爆炸的残余辐射制成的地图中寻找这种扭曲，称为宇宙微波背景（CMB）。然而，普朗克卫星的最新地图，我们在分析中发挥了重要作用，没有弦的直接证据。这并不意味着它们不在那里，尽管它们可能不在那里，但这确实意味着它们没有我们想象的那么大。然而，在剩余辐射的偏振中，它们还可以留下其他信号，我们打算获得宇宙弦和宇宙超弦在这样的图中留下的独特信号，然后搜索普朗克数据，看看它们是否潜伏在那里--这是弦论的第一个直接证据。现代物理学面临的关键问题之一是协调世纪物理学的两大支柱，即支配宏观尺度上物体运动的广义相对论和支配原子尺度上物体的量子力学。调和这些的努力被称为量子引力，在这个提议中，我们的目标是开发一些方法，并将其作为最终目标。

Our Universe is accelerating, distant galaxies move apart with ever increasing velocities, yet we don't know the source of this acceleration, referring to it as Dark Energy (DE). A key goal of our work is to pin down the nature of this enigmatic substance, including the possibility that it is signalling a breakdown of Einstein's description of gravity on the largest scales. The cosmological constant (CC) is the simplest DE candidate, yet the value it would have to have to be driving the acceleration is at least 60 orders of magnitude lower than we would naturally expect it to have based on the quantum theory of matter. As Pauli once observed, the electron's contribution to the CC should result in a universe no larger in size than the earth-moon distance ! We have developed two approaches to deal with the CC and will be analysing their cosmology. In both cases, we consider controlled deviations from Einstein's original model of gravity, allowing us to eliminate these dangerously large contributions to the CC. Alongside these models, we continue to ask questions about the nature of DE, and other novel long distance phenomena known as chameleons, developing new approaches to consider their effects on particles in accelerators, as well as on cold atoms in laboratory vacuum chambers. Dark matter (DM( is an illusive substance difficult to see because it does not interact electromagnetically, and yet it completely dominates the matter content of the Universe driving the dynamics of galaxies. There are currently two main ways we use to detect DM particles: one is deep underground in direct detection experiments where the particle collides with a nucleus of a heavy atom and the recoil of the nucleus is picked up in sensitive detectors, and the other is through the indirect measurements of decay products such as very high energy gamma rays that are produced as a result of DM particles annihilating in the sun. Up until now these two approaches have been somewhat exclusive of each other using different approaches to their analysis. In this proposal we intend to develop technology that will allow for the consistent comparison of direct and indirect detection data, thereby bringing these communities together and increasing the chance of detection. It is quite possible that the Early Universe was populated by two or more types of strings, fundamental strings whose modes of oscillations provide us with the particles we see today, and cosmic strings formed during phase transitions. Both of these strings would evolve as the universe expands and we can model their evolution. Because they are very massive (a km of cosmic string would have the mass of the moon for example), they perturb the spacetime in which they move leading to distortions in the temperature of the light in regions close to the strings. We search for this distortion in maps made from the remnant radiation from the Big Bang known as the Cosmic Microwave Background (CMB). However, the most recent maps from the Planck satellite, in which we have played an important role in analysing, there is no direct evidence of the strings. It doesn't mean they are not there, although they may not be, but it does mean they are not as massive as we thought. However, there are other signals they can leave in the polarisation of the remnant radiation and we intend to obtain the unique signals cosmic strings and cosmic superstrings would leave in such a map and then search the Planck data to see if they are found lurking in there - the first direct evidence of string theory. One of the key problems facing modern physics concerns reconciling two of the pillars of twentieth century physics, General Relativity which governs the motion of objects on macroscopic scales and Quantum Mechanics which governs objects on the atomic scale. The effort to reconcile these is known as Quantum Gravity and in this proposal we are aiming to develop a number of approaches with that as the ultimate goal.