Investigations in Gravitational Radiation

爱因斯坦的广义相对论（GR）预测，强引力场中的动力系统将以引力辐射的形式释放出大量的能量。引力波是时空结构中的涟漪，以光速从其源头传播，携带着关于其发射的物理过程的信息，这是无法通过其他方式获得的。它们是来自宇宙最深处的最难以捉摸的信号之一。旨在探测它们的实验已经发展了几十年，但直到现在，灵敏度才达到在几年内可能进行真实的探测的水平。全球干涉探测器网络包括德国-英国GEO 600、法国-意大利Virgo和美国激光干涉仪引力波天文台（LIGO）。这些探测器都达到了接近其设计目标的灵敏度，并获得了迄今为止最敏感的数据。不同项目之间的合作可以实现连续的数据采集，对大部分天空中的各种来源和现象具有灵敏度。来自GEO、LIGO和Virgo的数据已经开始影响我们对天文现象的理解。例如，这些探测器的最新观测结果表明：（a）克拉B脉冲星的辐射功率中只有不到2%是引力波，（B）排除了合并的双中子星是GR B 070201的祖先（如果它发生在M31中），（c）为随机引力波背景的强度设定了一个新的最佳上限。虽然目前阶段的观测（大约2010-2011年）有真实的机会产生第一个探测-可能来自紧凑的双星合并，但不能保证。然而，人们非常有信心，先进的探测器将定期观测引力波。卡迪夫和格拉斯哥小组已经发起并领导了对天文来源的搜索，这要归功于自八年前第一次数据采集运行开始以来一直支持的算法和分析工作。我们提出了一个继续改进GEO 600的方案，并将参与对地球观测组织和世界范围的干涉仪网络所产生的数据进行定性和分析。特别是，我们将进行搜索 * 合并中子星双星，中子星黑洞双星，黑洞双星 * 爆发的引力波，可能来自超新星，和 * 连续的信号从恒星和其他旋转中子星。与此同时，我们正在提议在探测器方面进行研究和开发。检测器灵敏度主要受到与反射镜的基板、反射涂层和悬挂元件相关的热噪声以及用于提供照明的光的量子性质所产生的噪声的限制。因此，我们的研究目标是在这些领域进行创新性改进。特别是，我们在二氧化硅悬浮液，光学和干涉测量领域的GEO和LIGO升级中发挥了主导作用，并在介电和波导镜涂层，硅衬底和低温悬浮液领域增强了Advanced LIGO计划和未来的干涉仪。综上所述，格拉斯哥、卡迪夫和斯特拉斯克莱德小组的目标是在其创新发展的基础上，率先使用探测器直接探测引力波。一旦实现这一里程碑，常规观测将帮助我们将这种辐射作为观测和理论工具，以了解 * 超新星和中子星的核心，* 伽马射线爆发发动机，* 黑洞和中子星的相互作用等。特别是，合并紧凑双星是自我校准的标准蜡烛，或警报器，这将成为宇宙学的一个新的精确工具，并将使广义相对论的强场测试成为可能。

Einstein's General Theory of Relativity (GR) predicts that dynamical systems in strong gravitational fields will release vast amounts of energy in the form of gravitational radiation. Gravitational waves are ripples in the fabric of spacetime and travel from their sources at the speed of light, carrying information about physical processes responsible for their emission, obtainable in no other way. They are among the most elusive signals from the deepest reaches in the Universe. Experiments aimed at detecting them have been in development for several decades, but only now are sensitivities reaching levels where real detection is possible within a few years. The worldwide network of interferometric detectors includes the German-UK GEO600, the French-Italian Virgo and the American Laser Interferometer Gravitational-Wave Observatory (LIGO). These detectors have all reached sensitivities close to their design goals and have taken the most sensitive data to date. Cooperation amongst different projects enables continuous data acquisition, with sensitivity to a wide range of sources and phenomena, over most of the sky. Data from GEO, LIGO and Virgo, has already begun to impact our understanding of astronomical phenomena. For example, the most recent observations with these detectors have (a) shown that less than 2% of the Crab pulsar's radiated power is in gravitational waves, (b) ruled out merging binary neutron stars as the progenitor of GRB 070201 (if it occurred in M31) and (c) set a new best upper limit on the strength of the stochastic gravitational-wave background. While the present phase of observations (circa 2010-2011) have a real chance of producing the first detections - possibly from compact binary coalescences, there can be no guarantees. However there is great confidence that the advanced detectors will routinely observe gravitational waves. The Cardiff and Glasgow groups have initiated and led searches for astronomical sources, thanks to the algorithmic and analysis effort that has been supported since the first data taking runs began eight years ago. We propose a programme of continued improvement to GEO600 and to be involved in the characterization and analysis of the resulting data from GEO and the worldwide network of interferometers. In particular we will be carrying out searches for * coalescing binary neutron stars, neutron star-black hole binaries, and black hole binaries * bursts of gravitational waves that may originate from supernovae, and * continuous signals from pulsars and other rotating neutron stars. In parallel, we are proposing research and development on the detector front. Detector sensitivity is mainly limited by thermal noise associated with the substrates of the mirrors, their reflective coatings, and their suspension elements, as well as by noise resulting from the quantum nature of the light used to provide illumination. Thus our research is targeted towards making innovative improvements in these areas. In particular we are taking leading roles in the upgrading of GEO and LIGO in the areas of silica suspensions, optics and interferometry, and for enhancements to the Advanced LIGO program and future interferometers in the areas of dielectric and waveguide mirror coatings, silicon substrates and cryogenic suspensions. In summary, the goal of the Glasgow, Cardiff and Strathclyde groups is to lead the first direct detection of gravitational waves using detectors based on their innovative developments. Once this milestone is achieved, routine observations will help us use this radiation as an observational and theoretical tool to understand * cores of supernovae and neutron stars, * gamma-ray burst engines, * the interactions of black holes and neutron stars, etc. In particular, coalescing compact binaries are self-calibrating standard candles, or sirens, which will be a new precision tool for cosmology and will enable strong field tests of general relativity.