Gravitational waves emitted by kinks on infinite strings are investigated using detailed estimations of the kink distribution on infinite strings. We find that gravitational waves from kinks can be detected by future pulsar timing experiments such as SKA for an appropriate value of the the string tension, if the typical size of string loops is much smaller than the horizon at their formation. Moreover, the gravitational wave spectrum depends on the thermal history of the Universe and hence it can be used as a probe into the early evolution of the Universe.
我们讨论宇宙弦的小尺度结构的一些迄今令人困惑的特征。我们认为，扭结起着关键作用，一个重要的量来研究是他们的锐度分布。特别地，我们建议，对于非常小的尺度，弦切向量的两点关联函数随着分离而线性变化，而不是像Polchinski和Rocha [Phys. Rev. D 74，083504（2006）]所提出的那样作为分数幂。然而，我们的结果与他们的结果是一致的，因为随着进化的进行，这种线性适用的尺度范围会缩小。
The nonlinear memory effect is a fascinating prediction of general relativity (GR), in which oscillatory gravitational-wave (GW) signals are generically accompanied by a monotonically-increasing strain which persists in the detector long after the signal has passed. This effect presents a unique opportunity to test GR in the dynamical and nonlinear regime. In this article we calculate the nonlinear memory signal associated with GW bursts from cusps and kinks on cosmic string loops, which are an important target for current and future GW observatories. We obtain analytical waveforms for the GW …
Stochastic gravitational waves from cosmic string loops in scaling
如果宇宙弦是在早期宇宙中形成的，它们的相关环在整个宇宙历史中发射引力波，并在所有频率上贡献于随机的引力波背景。我们提供了一个新的估计的随机引力波频谱考虑一个现实的宇宙循环分布，在缩放，因为它可以推断从南部-后藤数值模拟。我们的结果考虑了迄今为止忽略的各种影响。我们包括两个引力波发射和回反应的影响上的环分布，并表明，他们产生两个不同的功能的频谱。关于弦的微观结构，除了尖点和扭结的存在下，我们表明，由扭结碰撞产生的引力波爆发可能占主导地位的摆动弦的信号，这种情况可能是有利的，在最近的数值模拟。鉴于这些新的结果，我们提出了四个原型方案，剩余的理论不确定性的范围内，我们推导出相应的信号，并估计由LIGO和欧洲脉冲星定时阵列（EPTA）观测的弦张力的约束。在95%的置信度下，这些方案中约束较少的方案显示出弦线张力GU < 7.2 x 10^{-11}。每次振荡携带两个尖点的平滑回路验证了两西格玛界限GU < 1.0 x 10^{-11}，而所有场景中最受约束的描述了非常弯曲的回路，并在95%的置信度下满足GU < 6.7 x 10^{-14}。
We compare the spectrum of the stochastic gravitational wave background produced in several models of cosmic strings with the common-spectrum process recently reported by NANOGrav. We discuss theoretical uncertainties in computing such a background, and show that despite such uncertainties, cosmic strings remain a good explanation for the potential signal, but the consequences for cosmic string parameters depend on the model. Superstrings could also explain the signal, but only in a restricted parameter space where their network behavior is effectively identical to that of ordinary cosmic stri…
The motion of cosmic strings in the universe leads to the generation of wakes behind them. We study magnetized wakes of cosmic strings moving in the post recombination plasma. We show that magnetic reconnection can occur in the post shock region. Since the width of the cosmic string wake is very small, the reconnection occurs over a very short lengthscale. The reconnection leads to a large amount of kinetic energy being released in the post shock region of the cosmic string wake. This enhances the kinetic energy released during the reconnection. We make a rudimentary estimate of the kinetic en…
We investigate the contribution of cosmic string loops to the Cosmic Microwave Background (CMB) anisotropies. This is done by extending the Unconnected Segment Model (USM) to include the contribution of the cosmic string loops created throughout the cosmological evolution of a cosmic string network to the stress-energy tensor. We then implement this extended USM in the publicly available CMBACT code and obtain the linear CDM power spectrum and the CMB angular power spectra generated by cosmic string loops. We find that the shape of the angular power spectra generated by loops is, in general, s…
We study how the presence of world-sheet currents affects the evolution of cosmic string networks, and their impact on predictions for the cosmic microwave background (CMB) anisotropies generated by these networks. We provide a general description of string networks with currents and explicitly investigate in detail two physically motivated examples: wiggly and superconducting cosmic string networks. By using a modified version of the CMBact code, we show quantitatively how the relevant network parameters in both of these cases influence the predicted CMB signal. Our analysis suggests that pre…
