The DiRAC 2.5x Facility

天文学、核物理和粒子物理学界的物理学家都致力于从一个非常基本的层面上理解宇宙是如何运作的。从大型强子对撞机（Large Hadron Collider）实验探测到的原子核深处的最小距离，到在太空中发现的最大尺度星系团，它们工作的距离尺度相差50个数量级。然而，科学方面的挑战是通过以下问题联系起来的：宇宙是如何开始的？它是如何进化的？宇宙的基本成分和结构是什么？它们是如何相互作用的？进步需要新的天文观测和实验数据，但也需要新的理论见解。理论理解越来越多地来自大规模计算，它使我们能够非常准确地利用数据面对理论的结果，或者允许我们详细地询问数据以提取对我们的理论有影响的信息。这些计算测试了我们拥有的最快的计算机，并推动了这一领域的技术界限。他们还提供了一个良好的环境，培训学生在最先进的技术，代码优化和数据挖掘和可视化。DiRAC2高性能计算设施自2012年开始运行，为STFC支持的粒子物理、天文学、宇宙学和核物理等各个领域的理论研究提供计算资源。这是一个生产力很高的机构，每年在国际同行评审期刊上发表250多篇论文。然而，DiRAC2硬件现在至少有5年的历史，因此有很大的失败风险。失去任何一项DiRAC2服务都将对依赖它进行科学研究的研究团体产生潜在的灾难性影响。DiRAC2.5x项目申请资金的主要目的是取代达勒姆、爱丁堡和莱斯特的老化的DiRAC2硬件，同时利用最近的硬件进步提供一些新功能（例如使用闪存的i/o加速），作为拟议的DiRAC3服务的原型。DiRAC2.5x建立在DiRAC高性能计算设施的成功基础上，将在2018年为STFC支持的所有科学领域的前沿研究提供所需的资源。虽然需要资金来“维持照明”，但该科学项目将继续处于世界领先地位。将从这项投资中受益的项目包括：(i)从第一性原理计算基本粒子性质的晶格量子色动力学（QCD）；（ii）通过提高涉及夸克物质基本成分的罕见过程的理论预测的准确性，提高欧洲核子研究中心大型强子对撞机发现新物理的实验潜力；（iii）模拟产生引力波的黑洞对合并，例如LIGO联盟最近发现的引力波；（iv）迄今为止对宇宙中星系形成和演化最真实的模拟；(v)气体向超大质量黑洞的吸积，这是从物质中提取能量的最有效方法，也是推动星系形成和演化的引擎；（vi）利用欧洲空间局GAIA卫星的新数据校准我们银河系的新模型；（vii）太阳内部和行星内部的详细模拟；（viii）星团中恒星的形成——这将是第一次有可能跟踪比太阳大许多倍的恒星的形成。

Physicists across the astronomy, nuclear and particle physics communities are focussed on understanding how the Universe works at a very fundamental level. The distance scales with which they work vary by 50 orders of magnitude from the smallest distances probed by experiments at the Large Hadron Collider, deep within the atomic nucleus, to the largest scale galaxy clusters discovered out in space. The Science challenges, however, are linked through questions such as: How did the Universe begin and how is it evolving? and What are the fundamental constituents and fabric of the Universe and how do they interact?Progress requires new astronomical observations and experimental data but also new theoretical insights. Theoretical understanding comes increasingly from large-scale computations that allow us to confront the consequences of our theories very accurately with the data or allow us to interrogate the data in detail to extract information that has impact on our theories. These computations test the fastest computers that we have and push the boundaries of technology in this sector. They also provide an excellent environment for training students in state-of-the-art techniques for code optimisation and data mining and visualisation. The DiRAC2 HPC facility has been operating since 2012, providing computing resources for theoretical researchin all areas of particle physics, astronomy, cosmology and nuclear physics supported by STFC. It is a highly productivefacility, generating more than 250 papers annually in international, peer-reviewed journals. However, the DiRAC2 hardware is now at least 5 years old and is therefore at significant risk of failure. The loss of any one of the DiRAC2 serviceswould have a potentially disastrous impact on the research communities which rely on it to deliver their scientific research. The main purpose of the requested funding for the DiRAC2.5x project is to replace the ageing DiRAC2 hardware at Durham, Edinburgh and Leicesterwhile taking advantage of recent hardware advances to provide some new capabilities (e.g. i/o acceleration using flash storage) as prototypes forthe proposed DiRAC3 services. DiRAC2.5x builds on the success of the DiRAC HPC facility and will provide the resources needed to support cutting-edge research during 2018 in all areas of science supported by STFC. While the funding is required to "keep the lights on", the science programme will continue to beworld-leading. Examples of the projects which will benefit from this investment include:(i) lattice quantum chromodynamics (QCD) calculations of the properties of fundamental particles from first principles;(ii) improving the potential of experiments at CERN's Large Hadron Collider for discovery of new physics by increasing the accuracy of theoretical predictions for rare processes involving the fundamental constituents of matter known as quarks; (iii) simulations of the merger of pairs of black holes which generate gravitational waves such as those recently discovered by the LIGO consortium;(iv) the most realistic simulations to date of the formation and evolution of galaxies in the Universe;(v) the accretion of gas onto supermassive black holes, the most efficient means of extracting energy from matter and the engine which drives galaxy formation and evolution;(vi) new models of our own Milky Way galaxy calibrated using new data from the European Space Agency's GAIA satellite;(vii) detailed simulations of the interior of the sun and of planetary interiors;(viii) the formation of stars in clusters - for the first time it will be possible to follow the formation of stars many times more massive than the sun.