The Virgo consortium for cosmological supercomputer simulations

在过去的二十年里，我们看到了宇宙几何和物质含量的标准模型的出现，以及宇宙中所有结构的起源和演化。根据这个λ - cdm模型，我们生活在一个具有平坦几何形状的宇宙中，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的基本粒子，尚未在地球上直接探测到。只有5%是普通物质或重子物质，其中只有十分之一存在于恒星中，其余大部分存在于星系间气体中。在宇宙大爆炸的最初瞬间，宇宙质量密度中的量子涨落为结构埋下了种子。这些声波在近乎均匀的原始等离子体中产生微弱的声波，在宇宙大爆炸遗留下来的热量上留下了可观察到的印记，当时宇宙只有40万年的历史。通过对宇宙微波背景辐射的成像，这些微小的涟漪最终形成了我们今天所看到的丰富结构。正是这种从近乎均匀的原始汤到由星系、星系团和更大结构组成的宇宙网络的转变，才是这项应用的重点。重力，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随着宇宙膨胀而坍缩，形成今天的宇宙结构。这个过程很复杂，但可以用计算机模拟来计算。对于一组给定的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值的假设，模拟现在可以跟踪宇宙结构的形成历史，相当详细地跟踪暗物质、气体和恒星的演化。该应用程序为处女座联盟寻求计算资源，处女座联盟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，通常被认为是该领域的世界领先者。在过去的25年里，处女座联盟和前体合作在定义现代物理宇宙学方法和将Lambda-CDM建立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，每个主题都代表了计算天体物理学中的一个“重大挑战”。主题是：(1)暗物质宇宙；(2)气态宇宙；(3)第一批恒星和星系；(4)十亿秒差距尺度上的宇宙。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？它是如何进化的？”、“星系、恒星和行星是如何形成和演化的？”“我们的模拟课程有两个具体目标。首先是建立宇宙结构形成背后的物理过程，并在尚未经过测试的情况下探索LambdaCDM宇宙模型。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，并寻求从空间和地面设施（如钱德拉，xmm -牛顿，斯皮策，普朗克，赫舍尔，双子座，VLT和ALMA）的巨额投资中获得最大回报。

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.