Damping of gravitational waves by matter
Damping of gravitational waves by matter
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DOI：
10.1103/physrevd.96.084033
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发表时间：
2017-10-16
影响因子：
5
通讯作者：
Pethick, C. J.
中科院分区：
文献类型：
--
作者：
Baym, Gordon;Patil, Subodh P.;Pethick, C. J.
我们开发了一个统一的描述，通过玻尔兹曼方程，阻尼引力波的物质，包括碰撞。我们确定了两个物理上不同的阻尼机制碰撞和朗道阻尼。我们首先考虑平坦时空中的阻尼，然后将结果推广到宇宙膨胀。在第一个区域，引力波的最大碰撞阻尼，独立于物质中碰撞的细节，正如我们所展示的，只有当它的波长与视界的大小相当时才有意义。因此，除了原初引力辐射之外，星系际或星际物质对所有辐射的衰减都可以忽略不计。虽然物质的碰撞会导致剪切粘性，但它们也会消除各向异性应力，从而抑制引力波的衰减。原始引力波的衰减仍然是可能的。我们推广了温伯格的引力波阻尼计算，现在包括碰撞和粒子的有限质量，并解释碰撞限制的朗道阻尼。虽然引力波的朗道阻尼在平坦时空中不可能发生，但宇宙的膨胀通过传播给定波矢的引力波的频率而允许这种阻尼。
We develop a unified description, via the Boltzmann equation, of damping of gravitational waves by matter, incorporating collisions. We identify two physically distinct damping mechanisms-collisional and Landau damping. We first consider damping in flat spacetime, and then generalize the results to allow for cosmological expansion. In the first regime, maximal collisional damping of a gravitational wave, independent of the details of the collisions in the matter is, as we show, significant only when its wavelength is comparable to the size of the horizon. Thus damping by intergalactic or interstellar matter for all but primordial gravitational radiation can be neglected. Although collisions in matter lead to a shear viscosity, they also act to erase anisotropic stresses, thus suppressing the damping of gravitational waves. Damping of primordial gravitational waves remains possible. We generalize Weinberg's calculation of gravitational wave damping, now including collisions and particles of finite mass, and interpret the collisionless limit in terms of Landau damping. While Landau damping of gravitational waves cannot occur in flat spacetime, the expansion of the universe allows such damping by spreading the frequency of a gravitational wave of given wave vector.