arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0909.0287gr-qcastro-ph.HEhep-th
收藏

没有事件视界的引力波特征。I.薄壳引力星的非径向振荡

Gravitational wave signatures of the absence of an event horizon. I. Nonradial oscillations of a thin-shell gravastar

Paolo Pani, Emanuele Berti, Vitor Cardoso, Yanbei Chen, Richard Norte

摘要:

来自致密物体的引力波提供了有关其结构的信息,可以深入探测强引力区域。在这里,我们说明了事件视界的存在或不存在如何在超紧凑物体发射的引力波中产生质的差异。为了建立一个没有事件视界的稻草人超紧凑物体,但它在其他方面几乎与黑洞相同,我们考虑一个非旋转的薄壳模型的灵感来自Mazur和Mottola的引力星,它有一个史瓦西外部,德西特内部和一个无限薄的壳与有限的张力分离的两个区域。从外部时空来看,壳层可以任意接近史瓦西半径,所以当只对它的外部度规进行测试时,引力星似乎与黑洞没有区别。我们研究了系统的线性动力学,特别是连接内部和外部引力扰动的连接条件。作为第一个应用程序的形式主义,我们计算极轴振荡模式的薄壳引力星。我们证明了即使在表面红移变为无穷大的极限下,准正规模谱也完全不同于黑洞的谱。极性QNM依赖于壳层上物质的状态方程,可以用来区分不同的引力星模型。我们的计算表明,当壳层上的声速vs/c>0.92时,低致密引力星可能是不稳定的。

英文摘要:

Gravitational waves from compact objects provide information about their structure, probing deep into strong-gravity regions. Here we illustrate how the presence or absence of an event horizon can produce qualitative differences in the gravitational waves emitted by ultra-compact objects. In order to set up a straw-man ultra-compact object with no event horizon, but which is otherwise almost identical to a black hole, we consider a nonrotating thin-shell model inspired by Mazur and Mottola's gravastar, which has a Schwarzschild exterior, a de Sitter interior and an infinitely thin shell with finite tension separating the two regions. As viewed from the external space-time, the shell can be located arbitrarily close to the Schwarzschild radius, so a gravastar might seem indistinguishable from a black hole when tests are only performed on its external metric. We study the linearized dynamics of the system, and in particular the junction conditions connecting internal and external gravitational perturbations. As a first application of the formalism we compute polar and axial oscillation modes of a thin-shell gravastar. We show that the quasinormal mode spectrum is completely different from that of a black hole, even in the limit when the surface redshift becomes infinite. Polar QNMs depend on the equation of state of matter on the shell and can be used to distinguish between different gravastar models. Our calculations suggest that low-compactness gravastars could be unstable when the sound speed on the shell vs/c>0.92.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑