Exploring the Gravitational-wave Universe

引力波（GW）天文学的时代始于2015年，当时LIGO探测到双黑洞合并事件GW150914，这是人类观测到的能量最高的事件。这一惊人事件的宣布成为世界各地的头条新闻，并导致2017年诺贝尔物理学奖的颁发。随后又发现了更多的引力波，包括现在著名的与GRB170817A相关的双中子星合并事件GW170817，这是第一个多信使引力波事件。迄今为止，LIGO和VIRGO已经公布了15个高可信度探测的细节，并发布了50多个额外候选信号的公共警报。卡迪夫大学重力探测研究所（GEI）的研究人员为这些探测和打开引力波天空做出了重要贡献。总之，GEI的研究跨越了引力波天文学的整个广度，从基础研究到仪器，建模，探测和解释事件，以及对基础物理学，天体物理学和宇宙学的影响。GEI已经发展成为LIGO科学合作组织（LSC）的第四大组织，我们的成员通过一些关键的战略角色发挥领导作用。我们提出了一个雄心勃勃的计划，它将影响整个引力波天文学的广度。这包括开发未来探测器的先进技术，创建最精确的双黑洞信号模型，实时分析LIGO-Virgo-KAGRA数据的尖端技术，快速准确地描述源，并将引力波观测映射到天体物理学，宇宙学和基础物理学的新见解中。我们的实验项目侧重于升级当前LIGO探测器和下一代天文台的关键技术。我们将通过改进地震反馈控制系统和实施实时自适应控制来增加探测器的正常运行时间和数据质量。我们将开发更低损耗的方法，将LIGO中的噪声降低到标准量子极限以下，并探索同位干涉仪如何进一步提高灵敏度。我们将通过建立一个工作在更长波长的输入输出光学原型，为下一代低温探测器铺平道路，这需要探索新的激光器和光学器件。我们的建模、分析和天体物理项目将受益于项目之间的协同作用，产生更精确的源特征和天体物理解释。我们将对LIGO-Virgo的引力波数据进行最深入的分析，以寻找与GRB170817A等伽马射线爆发相对应的引力波。我们将利用机器学习技术来突破多信使天文学的极限，以亚秒级的延迟来检测一般的瞬态信号，如超新星、双星合并和吸积盘的不稳定性，使后续观测能够捕捉到这些事件中最早的电磁发射。不断提高的检测率将使我们能够进一步探索紧凑双星种群的参数空间，包括更多的罕见事件，但也需要更快的表征检测信号的手段。我们将开发半分析工具，以提供对参数估计的直观理解，从而能够及时识别异常事件。我们将实现在卡迪夫开创的完整、准确、快速的推理技术，并将其应用于中子星状态方程的推断。我们将进一步开发工具，从我们的观测中推断天体物理种群，并为种群模型提供实时更新。最后，我们将利用前所未有的数据集和双星群的物理驱动模型，将观测到的双星群与天体物理形成情景进行比较，以推断引力波的起源。

The era of gravitational-wave (GW) astronomy began in 2015 with LIGO's detection of the binary black-hole merger event GW150914, at the time the most energetic event ever observed by humanity. The announcement of this spectacular event generated headlines worldwide and led to the award of the 2017 Nobel Prize in Physics. More detections followed, including the now-famous binary neutron star merger event GW170817 associated with GRB170817A - the first multi-messenger gravitational-wave event. To date LIGO and VIRGO have published the details of 15 high-confidence detections and released public alerts for more than 50 additional candidate signals.Cardiff University researchers in the Gravity Exploration Institute (GEI) have made critical contributions to these detections and to the opening of the gravitational-wave sky. Together, the research of the GEI spans the entire breadth of gravitational-wave astronomy, from fundamental research into instruments, the modelling, detection and interpretation of events, and implications for fundamental physics, astrophysics, and cosmology. The GEI has grown to become the fourth largest group in the LIGO Scientific Collaboration (LSC), and our members provide leadership through a number of key strategic roles.We propose an ambitious programme that will have impacts across the breadth of gravitational-wave astronomy. This includes the development of advanced technology for future detectors, the creation of the most accurate state-of-the-art models for binary black hole signals, cutting edge techniques for real-time analysis of the LIGO-Virgo-KAGRA data, fast and accurate characterisation of sources, and mapping gravitational-wave observations into new insights into astrophysics, cosmology, and fundamental physics.Our experimental program focuses on technologies critical for upgrades to the current LIGO detectors and for next-generation observatories. We will increase the detector up-time and data quality by improving the seismic feedback control systems and implementing real time adaptive controls. We will develop lower-loss methods to reduce the noise in LIGO below the standard quantum limit and explore how co-located interferometers may further improve sensitivity. And we will pave the way for next-generation cryogenic detectors by building an input-output optics prototype operating at longer wavelengths, requiring the exploration of new lasers and optics.Our modelling, analysis, and astrophysics programme will benefit from synergy between the projects, yielding more precise source characterisation and astrophysical interpretations.We will perform the deepest analysis of the LIGO-Virgo data for gravitational-wave counterparts to gamma-ray bursts like GRB170817A. We will push the limits of multi-messenger astronomy by using machine learning techniques to detect generic transient signals such as supernovae, binary mergers, and accretion disk instabilities with sub-second latencies, enabling follow-up observations to catch the earliest electromagnetic emissions from these events.The ever increasing detection rates will allow us to explore further across the parameter space of compact binaries populations, including more rare events, but also require ever faster means of characterising detected signals. We will develop semi-analytical tools to provide an intuitive understanding of parameter estimation, allowing the prompt identification of exceptional events.We will implement complete, accurate, and fast inference techniques pioneered at Cardiff and apply then to infer neutron star equation of state. We will further develop tools to infer astrophysical populations from our observations and provide real-time updates to population models.Finally, we will compare the observed populations with astrophysical formation scenarios, exploiting the unprecedented data set and physically motivated models of binary populations, to infer the origins of gravitational waves.