旋转致密双星后牛顿轨道的引力波研究

本文利用辛算法和功率谱研究旋转致密双星保守的后牛顿哈密顿系统的引力辐射, 讨论了系统的动力学参量、旋转-轨道耦合、旋转-旋转耦合效 应及轨道类型对后牛顿近似引力波形的影响. 数值结果表明有序轨道的引力波随时间呈周期性地变化, 而混沌轨道引力波的变化具有混沌性, 并且轨道的混沌特性可提高引力波的辐射能量, 尤其指出的是旋转参量大小对引力波形的变化发挥至关重要的作用.     

半隐Euler法和隐中点法嵌入混合辛积分器的比较

当Hamilton函数分解为可积和不可积两部分时,前者能用分析方法给出解析解,而后者可借助一阶半隐Euler法或二阶隐中点法等数值求解,将这种解析和数值解法组合能构造二阶混合辛积分器.理论分析表明Euler嵌入法的稳定区要小于中点嵌入法的.再分别以圆形限制性三体问题和相对论自旋致密双星后牛顿Hamilton构型为例,详细比较了两嵌入法的性能特点.二者的数值精度、稳定性及计算效率与Hamilton的分解方式和轨道类型有关.就圆形限制性三体问题而言,当Hamilton采用势能和含坐标与动量混合项在内的动能分解 关键词： 辛积分器 后牛顿近似 自旋致密双星 混沌     

引力、引力波和引力波的探测

简要地回顾了引力和引力波概念的由来,以及人们为探测引力波所作的各种努力．     

引力波与广义相对论

介绍了引力波的广义相对论理论基础.介绍如何通过双星周期的时间改变间接检测引力辐射,如何利用引力波的偏振效应直接检测引力波.     

引力波与引力波探测

 一、引力波探测的主要背景引力波是爱因斯坦和其他物理学家提出的关于广义相对论的四大预言之一,未来在引力波探测的研究中所获得的突破,将可能比其他预言产生更为巨大而深远的影响,甚至大大促进人类文明的进程。1916年爱因斯坦发表了他的广义相对论,并在该理论的基础上预言了引力波的存在。到目前为止,广义相对论一些重大预言都被实验证实了,它们包括水星近日点的进动、光线在引力场中的弯曲、光谱线在引力场中的频移,以及由此而延伸的关于雷达回波的延迟等。这些成果又进一步推进了相对论在天文观测、相对论天体物理、宇宙学甚至高能物理和广义相对论的交叉领域等方面的应用。     

1993年诺贝尔物理学奖获奖项目——脉冲双星与引力波

 脉冲星和中子星1967年,英国剑桥大学的天文学家安东尼·休伊什(Antony Hewish)和他的一位年轻女研究生乔斯林·贝尔(Jocelyn Bell)一起,用他们的射电望远镜偶然记录到一种来自某个天体的射电脉冲信号。     

漫谈引力波探测

爱因斯坦广义相对论成功地预言了行星进动、引力红移、光线偏折、回波延迟等物理事实，而“存在引力波”是爱因斯坦广义相对论的另一重大预言。根据广义相对论，我们从爱因斯坦广义相对论引力场方程的弱场近似可以得到线性近似的引力波解；引力波是横波，能以光速穿过真空；引力波非常容易产生，但是非常的弱如果让一根长为20米，直径为1.6米，重500吨的圆棒以能够使自身断裂的极限速度（每秒28转）围绕自身中心点高速转动，它发射的引力波功率也不过只有2.2×10^-19瓦，因此，对引力波的探测极其困难。     

捕捉引力波

 一、足够精确的牛顿引力理论在宏观物理世界中,引力是一种主要的作用。太阳东升西坠,地球四季交替,海水潮涨潮落,众多自然现象都受到引力的支配。1687年,牛顿在前人的研究基础上,导出了万有引力定律。利用万有引力定律可以圆满地解释哥白尼的学说和开普勒的行星运动三定律。牛顿引力理论的精彩之处还有准确地预言了海王星和冥王星的存在,指导天文学家成功地发现了这两颗太阳行星。按牛顿的引力理论,两物体间的引力作用是瞬间完成的。但爱因斯坦认为,光速是任何作用的极限速度,因此引力作用不可能在瞬间实现。1905年,爱因斯坦发表著名的历史文献《论动体的电动力学》,建立了狭义相对论。在以后     

致密双星后牛顿偏心轨道的引力波研究

本文主要研究非保守的后牛顿哈密顿自旋致密双星偏心轨道的引力辐射,数值比较保守的和非保守的自旋致密双星系统轨道参量偏心率大小与 引力波形的关系及引力辐射耗散效应项对轨道动力特性的影响. 数值研究表明：由于系统能量积分被保持,保守的双星轨道偏心率值改变对时域引力波形变化影响不是很明显,但辐射的引力波频率分布范围随着偏心率的增大而扩大. 而当运动方程中包含2.5PN引力耗散效应项时,由于引力辐射时伴随着能量和角动量损失,导致双星两体之间的距离和轨道偏心率逐渐衰减,轨道动力特性变得更加复杂. 双星旋进合并过程中辐射的引力波受到轨道偏心率的调制,引力辐射的强度随着偏心率的增大而增强,而引力辐射持续的时间缩短,且自旋与自旋耦合效应项对引力的贡献增大了. 关键词： 非保守的 引力辐射 耗散 偏心率     

引力波和引力透镜

 引力是物质世界的一种客观属性。大科学家牛顿以精确的数字形式表达了万有引力定律,建立了人类对引力认识的第一座里程碑。后来,牛顿引力理论对解释一些天体物理问题却遇到了困难。爱因斯坦于1916年提出了著名的广义相对论,其中预言宇宙中存在着“引力波”。引力波即引力的波动,它与引力的强弱变化有关。引力波可由加速运行的物质产生,其传播速度应等于光速。在理论上,任何运动的物质都会产生引力波。比如,如果你把一只台球悬挂起来,使它像打秋千似的荡来荡去,当它荡到比较靠近你时,其引力作用比离你较远时更为大些,就形成引力波。换句话说,球的摆动,使它的引力发生一种像波那样起伏的变化。     

Estimation of parameters of gravitational waves from coalescing binaries

In this paper we deal with the measurement of parameters of the gravitational wave signal emitted by a coalescing binary system of compact stars. We present the results of Monte Carlo simulations carried out for initial LIGO, incorporating the first post-Newtonian corrections to the waveform. Using the parameters so determined, we estimate the direction to the source. We stress the use of the time-of-coalescence rather than the time-of-arrival of the signal to determine the direction of the source. We show that this can considerably reduce the errors in the determination of the direction of the source.     

Equations of motion of compact binaries at the third post-Newtonian order

The equations of motion of two point masses in harmonic coordinates are derived through the third post-Newtonian (3PN) approximation. The problem of selffield regularization (necessary for removing the divergent self-field of point particles) is dealt with in two separate steps. In the first step the extended Hadamard regularization is applied, resulting in equations of motion which are complete at the 3PN order, except for the occurrence of one and only one unknown parameter. In the second step the dimensional regularization (ind dimensions) is used as a powerful argument for fixing the value of this parameter, thereby completing the 3-dimensional Hadamard-regularization result. The complete equations of motion and associated energy at the 3PN order are given in the case of circular orbits.     

Very high-frequency gravitational waves from magnetars and gamma-ray bursts

Extremely powerful astrophysical electromagnetic(EM) systems could be possible sources of highfrequency gravitational waves(HFGWs). Here, based on properties of magnetars and gamma-ray bursts(GRBs), we address "Gamma-HFGWs"(with very high-frequency around 10~(20) Hz) caused by ultra-strong EM radiation(in the radiation-dominated phase of GRB fireballs) interacting with super-high magnetar surface magnetic fields(～10~(11) T).By certain parameters of distance and power, the Gamma-HFGWs would have far field energy density ?gw around10~(-6), and they would cause perturbed signal EM waves of～10~(-20) W/m~2 in a proposed HFGW detection system based on the EM response to GWs. Specially, Gamma-HFGWs would possess distinctive envelopes with characteristic shapes depending on the particular structures of surface magnetic fields of magnetars, which could be exclusive features helpful to distinguish them from background noise. Results obtained suggest that magnetars could be involved in possible astrophysical EM sources of GWs in the very high-frequency band, and Gamma-HFGWs could be potential targets for observations in the future.     

Improved calculation of relic gravitational waves

In this paper, we have improved the calculation of the relic gravitational waves (RGW) in two aspects. First, we investigate the transfer function by taking into consideration the redshift-suppression effect, the accelerating expansion effect, the damping effect of free-streaming relativistic particles, and the damping effect of cosmic phase transition, and give a simple approximate analytic expression, which clearly illustrates the dependence on the cosmological parameters. Second, we develop a numerical method to calculate the primordial power spectrum of RGW in a very wide frequency range, where the observed constraints on $n_{\rm s}$ (the scalar spectral index) and $P_{\rm S}(k_0)$ (the amplitude of primordial scalar spectrum) and the Hamilton--Jacobi equation are used. This method is applied to two kinds of inflationary models, which satisfy the current constraints on $n_{\rm s}$, $\alpha$ (the running of $n_{\rm s}$) and $r$ (the tensor--scalar ratio). We plot them in the $r-{\it\Omega}_{\rm g}$ diagram, where ${\it\Omega}_{\rm g}$ is the strength of RGW, and study their measurements from the cosmic microwave background (CMB) experiments and laser interferometers.     

Primordial black holes and third order scalar induced gravitational waves

The process of primordial black hole (PBH) formation is inevitably accompanied by scalar induced gravitational waves (SIGWs). The strong correlation between PBH and SIGW signals may offer a promising approach to detecting PBHs in upcoming gravitational wave experiments, such as the Laser Interferometer Space Antenna (LISA). We investigate third order SIGWs during a radiation-dominated era in the case of the monochromatic primordial power spectrum \begin{document}$ \mathcal{P}_{\zeta}=A_{\zeta}k_*\delta\left(k-k_*\right) $\end{document}. For LISA observations, the relationships between the signal-to-noise ratio (SNR) and monochromatic primordial power spectrum are studied systematically, revealing that the effects of third order SIGWs extend the cutoff frequency from \begin{document}$ 2f_* $\end{document} to \begin{document}$ 3f_* $\end{document} and lead to an approximately 200% increase in the SNR for the frequency band from \begin{document}$ 10^{-5} $\end{document}Hz to \begin{document}$ 1.6\times 10^{-3} $\end{document}Hz, corresponding to PBHs with masses in the range \begin{document}$4\times 10^{-12}M_{\odot} \sim 10^{-7}M_{\odot}$\end{document}. We find that there is a critical value, \begin{document}$ A_*=1.76\times 10^{-2} $\end{document}, for the amplitude of the monochromatic primordial power spectra, such that when \begin{document}$ A_{\zeta}>A_* $\end{document}, the energy density of third order SIGWs is larger than that of second order SIGWs.     

The gravitational wave symphony of the Universe

The new millennium will see the upcoming of several ground-based interferometric gravitational wave antennas. Within the next decade a space-based antenna may also begin to observe the distant Universe. These gravitational wave detectors will together operate as a network taking data continuously for several years, watching the transient and continuous phenomena occurring in the deep cores of astronomical objects and dense environs of the early Universe where gravity was extremely strong and highly nonlinear. The network will listen to the waves from rapidly spinning non-axisymmetric neutron stars, normal modes of black holes, binary black hole inspiral and merger, phase transitions in the early Universe, quantum fluctuations resulting in a characteristic background in the early Universe. The gravitational wave antennas will open a new window to observe the dark Universe unreachable via other channels of astronomical observations.