This review is focused on tests of Einstein's theory of General Relativity with gravitational waves that are detectable by ground-based interferometers and pulsar timing experiments. Einstein's theory has been greatly constrained in the quasi-linear, quasi-stationary regime, where gravity is weak and velocities are small. Gravitational waves will allow us to probe a complimentary, yet previously unexplored regime: the non-linear and dynamical strong-field regime. Such a regime is, for example, applicable to compact binaries coalescing, where characteristic velocities can reach fifty percent the speed of light and compactnesses can reach a half. This review begins with the theoretical basis and the predicted gravitational wave observables of modified gravity theories. The review continues with a brief description of the detectors, including both gravitational wave interferometers and pulsar timing arrays, leading to a discussion of the data analysis formalism that is applicable for such tests. The review ends with a discussion of gravitational wave tests for compact binary systems.
Gravitational waves provide a new probe of the Universe which can reveal a number of cosmological and astrophysical phenomena that cannot be observed by electromagnetic waves. Different frequencies of gravitational waves are detected by different means. Among them, precision measurements of pulsar timing provides a natural detector for gravitational waves with light-year scale wavelengths. In this review, first a basic framework to detect a stochastic gravitational wave background using pulsar timing array is introduced, and then possible interpretations of the latest observational result of 1…
The coherent oscillation of ultralight dark matter in the mass regime around $10^{-23}$ eV induces changes in gravitational potential with the frequency in the nanohertz range. This effect is known to produce a monochromatic signal in the pulsar timing residuals. Here we discuss a multifield scenario that produces a wide spectrum of frequencies, such that the ultralight particle oscillation can mimic the pulsar timing signal of stochastic common spectrum process. We discuss how ultralight dark matter with various spins produces such a wide band spectrum on pulsar timing residuals and perform t…
Pulsar timing experiments are currently searching for gravitational waves, and this dissertation focuses on the development and study of the pulsar timing residual models used for continuous wave searches. The first goal of this work is to re-present much of the fundamental physics and mathematics concepts behind the calculations and theory used in pulsar timing. While there exist many reference sources in the literature, I try to offer a fully self-contained explanation of the fundamentals of this research which I hope the reader will find helpful. The next goal broadly speaking has been to f…
We study the observation of stochastic gravitational-wave background (SGWB) made by pulsar-timing arrays in the spherical harmonic space. Instead of using the Shapiro time delay, we keep the Sachs-Wolfe line-of-sight integral for the timing residual of an observed pulsar. We derive the power spectrum of the timing residual, from which the overlap reduction functions and the bipolar spherical harmonics coefficients are constructed for the SGWB intensity and polarization anisotropies. We have reproduced the previous results, noting that we have developed a fast algorithm for computing accurate o…
Detecting Chiral Gravitational Wave Background with a Dipole Pulsar Timing Array
National Astronomical Observatories, Chinese Academy of Sciences(中国科学院国家天文台);Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences(中国科学院大学杭州高等研究院);School of Astronomy and Space Science, University of Chinese Academy of Sciences(中国科学院大学天文与空间科学学院);Institute of Fundamental Physics and Quantum Technology, Ningbo University(宁波大学基础物理与量子技术研究所);Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo(东京大学宇宙木理论研究所);Asia Pacific Center for Theoretical Physics(亚太理论物理中心);Leung Center for Cosmology and Particle Astrophysics, National Taiwan University(台湾大学梁氏宇宙学与粒子天体物理学研究中心);Yukawa Institute for Theoretical Physics, Kyoto University(京都大学汤川理论物理研究所)
Pulsar timing-array correlation measurements offer an exciting opportunity to test the nature of gravity in the cosmologically novel nanohertz gravitational wave regime. The stochastic gravitational wave background is assumed Gaussian and random, while there are limited pulsar pairs in the sky. This brings theoretical uncertainties to the correlation measurements, namely the pulsar variance due to pulsar samplings and the cosmic variance due to Gaussian signals. We demonstrate a straightforward calculation of the mean and the variances on the Hellings-Downs correlation relying on a power spect…
Why Gravitational Wave Science Needs Pulsar Timing Arrays And Why Pulsar Timing Arrays Need Both Arecibo and the GBT: A Response to the NSF-AST Portfolio Review from the NANOGrav Collaboration
A Realistic Pulsar -- Supermassive Black Hole Timing Model
Peking University(北京大学);Kavli Institute for Astronomy and Astrophysics, Peking University(北京大学科维理天文与天体物理研究所);National Astronomical Observatories, Chinese Academy of Sciences(中国科学院国家天文台)
Non-Gaussian timing residual skewness in pulsar timing arrays
Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Leibnitz Universität Hannover(马克斯·普朗克引力物理研究所(爱因斯坦研究所),莱布尼茨汉诺威大学);Department of Physics, National Central University(国立中央大学物理系);Institute of Physics, Academia Sinica(台湾中央研究院物理研究所);Institute of Astronomy and Astrophysics, Academia Sinica(台湾中央研究院天文及天文物理研究所)
Millisecond and Binary Pulsars as Nature's Frequency Standards. III. Fourier Analysis and Spectral Sensitivity of Timing Observations to Low-Frequency Noise
The detection of a stochastic background of low-frequency gravitational waves by pulsar-timing and astrometric surveys will enable tests of gravitational theories beyond general relativity. These theories generally permit gravitational waves with non-Einsteinian polarization modes, which may propagate slower than the speed of light. We use the total-angular-momentum wave formalism to derive the angular correlation patterns of observables relevant for pulsar timing arrays and astrometry that arise from a background of subluminal gravitational waves with scalar, vector, or tensor polarizations. …
CENTRA, Departamento de Física, Instituto Superior Técnico – IST Universidade de Lisboa – UL(里斯本大学高级技术学院物理系中心);Departamento de Física Fundamental, Universidad de Salamanca(萨拉曼卡大学基础物理系);Insituto Universitario de Física Fundamental y Matemáticas (IUFFyM), Universidad de Salamanca(萨拉曼卡大学基础物理与数学大学研究所)
We provide an observation method for gravitational waves using a pulsar timing array to extend the observational frequency range up to the rotational frequency of pulsars. For this purpose, we perform an analysis of a perturbed electromagnetic wave in perturbed spacetime from the field perspective. We apply the analysis to the received electromagnetic waves in a radio telescope, which partially composes the periodic electromagnetic pulse emitted by a pulsar. For simple observation, two frequency windows are considered. For each window, we propose gauge-invariant quantities and discuss their ob…
Searching for gravitational waves from the Crab pulsar - the problem of timing noise
蟹状星云脉冲星(B 0531 +21)是目前已知的最有希望的引力波源之一。蟹状星云相对较大的定时噪声导致其相位演化偏离简单的自旋下降模型。在对蟹状星云脉冲星进行时域搜索时,需要考虑这种影响,以避免搜索效率的严重下降。Jodrell Bank Crab脉冲星星历表的检查,看看它是否可以用于跟踪相位演化的任何引力波信号从脉冲星,我们提出了一种外差的数据,考虑到相位漂移的方法。从电磁和引力观测的定时噪声的比较获得有关脉冲星的物理信息的可能性进行了讨论。最后,脉冲星毛刺所造成的其他问题进行了讨论。
Pulsar timing array signals induced by black hole binaries in relativistic eccentric orbits
非圆轨道上的单个超大质量黑洞双星可能是快速成熟的脉冲星定时阵列实验的纳赫兹引力波源。我们发展了一种精确有效的方法来计算脉冲星定时阵列信号,由于引力波从吸入相对论偏心轨道的超大质量黑洞双星。我们的方法采用开普勒型参数解模型的第三后牛顿精确进动偏心轨道,而一个新的半解析处方提供了模型的四极阶引力波发射的影响。这些输入导致一个半解析的处方来模拟这样的信号,引起的非自旋黑洞二进制沿任意偏心率轨道螺旋。此外,我们提供了一个完整的分析处方模型脉冲星定时阵列信号从黑洞二进制沿适度偏心轨道吸气,Boetzelet等人的影响。[Phys. Rev. D 96,044011(2017)]。这些方法正在被纳入企业和TEMPO 2搜索脉冲星定时阵列数据集中存在这样的二进制文件。
We study the observation of polarized stochastic gravitational-wave background (SGWB) in pulsar-timing-array experiments. The time residual for an observed pulsar is formulated as a line-of-sight integral that incorporates the effects of the pulsar term, from which we construct the correlation function of the time residual between a pair of pulsars in terms of the overlap reduction functions (ORFs) for the SGWB intensity and polarization anisotropies. Our formulation provides a numerical scheme for computing the ORFs for high multipole moments and the lowest-moment ORFs for the SGWB linear pol…
Over the last few years, a set of new results from pulsar timing has introduced much tighter constraints on violations of the strong equivalence principle (SEP), either via a direct verification of the universality of free fall for a pulsar in a triple star system, or from tests of the nature of gravitational waves, in particular a search for dipolar gravitational wave emission in a variety of binary pulsars with different masses. No deviations from the SEP have been detected in our experiments. These results introduce some of the most stringent constraints on several classes of alternative th…