Gravitational wave astronomy: the current status
In the centenary year of Einstein's General Theory of Relativity, this paper reviews the current status of gravitational wave astronomy across a spectrum which stretches from attohertz to kilohertz frequencies. Sect. 1 of this paper reviews the historical development of gravitational wave astronomy from Einstein's first prediction to our current understanding the spectrum. It is shown that detection of signals in the audio frequency spectrum can be expected very soon, and that a north-south pair of next generation detectors would provide large scientific benefits. Sect. 2 reviews the theory of gravitational waves and the principles of detection using laser interferometry. The state of the art Advanced LIGO detectors are then described. These detectors have a high chance of detecting the first events in the near future. Sect. 3 reviews the KAGRA detector currently under development in Japan, which will be the first laser interferometer detector to use cryogenic test masses. Sect. 4 of this paper reviews gravitational wave detection in the nanohertz frequency band using the technique of pulsar timing. Sect. 5 reviews the status of gravitational wave detection in the attohertz frequency band, detectable in the polarisation of the cosmic microwave background, and discusses the prospects for detection of primordial waves from the big bang. The techniques described in sects. 1–5 have already placed significant limits on the strength of gravitational wave sources. Sects. 6 and 7 review ambitious plans for future space based gravitational wave detectors in the millihertz frequency band. Sect. 6 presents a roadmap for development of space based gravitational wave detectors by China while sect. 7 discusses a key enabling technology for space interferometry known as time delay interferometry.
© 2015 Science China Press and Springer-Verlag Berlin Heidelberg. Received September 24, 2015; accepted September 28, 2015. The authors thank the Kavli Institute for Theoretical Physics, China for funding the Next Detectors for Gravitational Astronomy Program, and for their hospitality. Sect. 2 is based on DR's talks given during the course of this program. DR and KA are supported by the US National Science Foundation (Grant No. PHY-0757058), FZ is supported by the National Natural Science Foundation of China (Grant Nos. 11443008 and 11503003), a Returned Overseas Chinese Scholars Foundation grant, and Fundamental Research Funds for the Central Universities (Grant No. 2015KJJCB06). XZ, LW and GH acknowledge funding support from the Australian Research Council. This work was supported by the National Space Science Center, Chinese Academy of Sciences (Grant Nos. XDA04070400 and XDA04077700). Prof. HU WenRui's effort to promote GW detection in space in China motivated our study in the first place. We are also grateful to Prof. ZHANG ShuangNan for his support throughout the course of our work. Professors YAU Shing-Tung and YANG Lo have been very supportive and the Morningside Center of Mathematics provides a very conductive research environment to carry out the study. Partial supports from the National Natural Science Foundation of China (Grant Nos. 11305255, 11171329 and 41404019).