The Virgo consortium for cosmological supercomputer simulations

在过去的20年里，我们已经看到了一个标准模型的出现，这个模型描述了我们宇宙的几何形状和物质组成，以及宇宙中所有结构的起源和演化。根据这个Lambda-CDM模型，我们生活在一个几何形状平坦的宇宙中，其中至少三分之二的质量-能量现在以暗能量场的形式存在，这导致宇宙以不断增加的速度膨胀。大约四分之一是暗物质，很可能是一种新的弱相互作用基本粒子，尚未在地球上直接检测到。只有大约5%是普通的，或重子物质，其中只有大约十分之一在今天的恒星中，其余的主要存在于星系际气体中。在大爆炸的最早时刻，量子涨落就在宇宙的质量密度中留下了印记，从而孕育了结构。它们在近乎均匀的原始等离子体中产生微弱的声波，这些声波在宇宙只有40万年的时候发出的大爆炸遗留下来的热量上留下了可观察到的印记。这些微小的涟漪，通过对宇宙微波背景辐射的成像而绘制出来，最终发展成为我们今天在我们周围看到的丰富的结构。正是这种从近乎均匀的原始汤到星系、星系团和更大结构的宇宙网的转变，是这一应用的重点。引力，主要是由于暗物质，放大了微小的原始涟漪，导致暗物质和气体块停止与宇宙一起膨胀，并坍塌形成今天的宇宙结构。这个过程很复杂，但可以通过计算机模拟来计算。对于给定的一组假设，关于早期宇宙中不均匀性的产生，暗物质的身份和宇宙学参数的值，模拟现在可以遵循宇宙结构的形成历史，跟踪暗物质，气体和恒星的演化，相当详细。该应用程序为Virgo财团寻求计算资源，Virgo财团是一个由英国领导的国际合作组织，从事结构形成的超级计算机模拟，并被公认为该主题的世界领导者。在过去的25年里，Virgo联盟和先驱合作在定义物理宇宙学的现代方法和建立Lambda-CDM作为标准模型方面发挥了核心作用。我们的计划可以分为四个广泛的，相互关联的主题，每一个都代表了计算天体物理学的“大挑战”。主题是：（1）暗物质宇宙;（2）气体宇宙;（3）第一颗恒星和星系;（4）千兆秒差距尺度的宇宙。因此，我们的计划针对STFC路线图中九个关键科学问题中的第一个和第五个：“宇宙是由什么组成的，它是如何演化的？”星系、恒星和行星是如何形成和演化的？"我们的模拟计划有两个具体目标。第一个是建立宇宙结构形成的物理过程，并在尚未测试的制度中探索LambdaCDM宇宙学模型。第二个目标是在理论和观测之间架起一座桥梁。模拟是从宇宙学和天体物理学理论中提取和检验可观测预测的最佳手段，通常也是唯一的手段。因此，我们的计划与英国和整个欧洲的观测计划紧密结合，并寻求最大限度地提高对钱德拉、XMM-牛顿、斯皮策、普朗克、赫歇尔、双子座、VLT和阿尔马等空间和地面设施的巨额投资的回报。

The last twenty years have seen the emergence of a standard model for the geometry and material content of our Universe, as well as for the origin and evolution of all structure within it. According to this Lambda-CDM model, we live in a universe with a flat geometry where at least two thirds of all mass-energy is now in the form of a dark energy field which is causing the universe to expand at an ever increasing rate. About a quarter is dark matter, most probably a new weakly interacting elementary particle yet to be detected directly on Earth. Only about 5% is ordinary, or baryonic, matter of which only about a tenth is in stars today and the rest resides mostly in intergalactic gas. Structure was seeded by quantum fluctuations imprinted in the mass density of the universe at the very earliest instants of the Big Bang. These produced weak sound waves in the near-uniform primordial plasma that left observable imprints on the heat left over from the Big Bang, emitted when the universe was only 400,000 years old. These tiny ripples, mapped by imaging the cosmic microwave background radiation, eventually grew into the full richness of structure we see around us today. It is this transformation from a near-uniform primordial soup to a cosmic web of galaxies, clusters and larger structures that is the focus of this application. Gravity, mostly due to dark matter, amplifies the tiny primordial ripples, causing lumps of dark matter and gas to stop expanding with the universe and collapse to form today's cosmic structures. This process is complex, but it can be calculated using computer simulations. For a given a set of assumptions regarding the generation of inhomogeneities in the early universe, the identity of the dark matter, and the values of the cosmological parameters, simulations can now follow the formation history of cosmic structure, tracking the evolution of dark matter, gas and stars, in considerable detail. This application seeks computing resources for the Virgo consortium, a UK-led international collaboration engaged in supercomputer simulations of the formation of structure and generally recognized as the world leader in the subject. Over the past 25 years, the Virgo consortium and precursor collaborations have played a central role in defining the modern approach to physical cosmology and establishing Lambda-CDM as the standard model. Our programme can be divided into four broad, interrelated themes, each of which represents a 'Grand Challenge' in computational astrophysics. The themes are: (1) the dark matter universe; (2) the gaseous universe; (3) the first stars and galaxies; (4) the universe on gigaparsec scales. Our programme thus targets the first and fifth of the nine key science questions in the STFC roadmap: 'What is the universe made of and how does it evolve?', 'How do galaxies, stars and planets form and evolve?'' Our simulation programme has two specific aims. The first is to establish the physical processes that underlie the formation of cosmic structure and explore the LambdaCDM cosmological model in as yet untested regimes. The second goal is to provide a bridge between theory and observations. Simulations are the best, often the only, means to extract and test observable predictions from cosmological and astrophysical theory. Thus, our programme is closely integrated with observational initiatives in the UK and across Europe and seeks to maximize the return from the huge investments being made in space- and ground-based facilities such as Chandra, XMM-Newton, Spitzer, PLANCK, Herschel, Gemini, VLT, and ALMA.