Gravitational radiation from supernova neutrino bursts
Gravitational radiation from supernova neutrino bursts
复制标题
超新星中微子爆发的引力辐射
作者：
M. Turner
超新星，大质量恒星剧烈坍缩成中子星，被认为是已知最强的引力辐射源。下落物质的流体动力学运动的四极矩（或更高）产生辐射。总能量为10.1 M\circ c2，持续时间在1010 −3和1 s之间的中微子爆发被认为伴随着中微子1。如果这个爆发具有非球形的角分布，它将产生额外的引力辐射-可能与坍缩引起的辐射相当。中微子爆发可能产生引力波一直被忽视，直到最近爱泼斯坦提出了这个想法。这个问题本身就很有趣，因为无质量场是辐射场的源。在电磁学中，不存在带电的无质量粒子;事实上，这种粒子的存在会导致红外发散。中微子的引力效应以前已经研究过2，4-6，但我们在这里报告的方法是新的，在电磁学中有很好的类似物。中微子的发射是一个量子过程，因此我们使用温伯格3的零频率极限（ZFL）量子技术来获得一个经典的源，它给出了正确的结果在这个极限。由于爆发的时间尺度（10− 10 - 3-1 s）比中微子发射过程的时间尺度（10−22 s）长得多，因此计算中只需要ZFL。ZFL技术已经以类似的方式在电磁学中用于计算伴随β衰变或电子捕获的电磁辐射7。Smarr将ZFL方法应用于引力韧致辐射过程8。
SUPERNOVAE, the violent collapses of massive stars into neutron stars, are considered to be the strongest known sources of gravitational radiation. The quadrupole (and higher) moments of the hydrodynamic motions of the infalling matter generate the radiation. A burst of neutrinos of total energy ∼0.1 M\cirċc2 and of duration between ∼10−3 and 1 s is thought to accompany the collapse1. If this burst has nonspherical angular distribution, it will generate additional gravitational radiation— possibly comparable in magnitude to that caused by the collapse. That the neutrino burst might produce gravitational waves had been overlooked until recently, when Epstein suggested the idea2. This problem is of interest in its own right because a massless field is acting as the source of a radiation field. In electromagnetism there are no charged, massless particles; in fact, the existence of such a particle would lead to infrared divergences3. The gravitational effects of neutrinos have been studied previously2,4–6, but the approach we report here is new and has a nice analogue in electromagnetism. The emission of a neutrino is a quantum process and so we use the zero frequency limit (ZFL) quantum technique of Weinberg3 to obtain a classical source which gives correct results in this limit. Because the time scale of the burst (∼10−3–1 s) is much longer than that of the neutrino emission process (∼10−22 s) only the ZFL is needed in the calculation. The ZFL technique has been used in an analogous way in electromagnetism to calculate the electromagnetic radiation accompanying β-decay or electron capture7. Smarr has applied the ZFL method to the gravitational bremsstrahlung process8.