Loop decay in Abelian-Higgs string networks
Loop decay in Abelian-Higgs string networks
复制标题
阿贝尔-希格斯弦网络中的循环衰减
DOI：
10.1103/physrevd.104.043519
复制
发表时间：
2021
影响因子：
5
通讯作者：
J. Urrestilla
中科院分区：
文献类型：
--
作者：
M. Hindmarsh;J. Lizarraga;Ander Urio;J. Urrestilla
我们研究阿贝尔-希格斯模型中宇宙弦环的衰变。我们证实了早期的结果，即由随机场初始条件形成的无限字符串的交集形成的循环很快就会消失，其寿命与其初始静止帧长度“init”成正比。我们研究了一个具有高达 6000 个反质量单位的群体，并测量比例常数为 0.14±0.04，与初始长度无关。我们提出了一种新方法，从最初静止的弦构造振荡非自相交循环，并表明相比之下，这些循环的生命周期大约与“init”一样缩放，这与之前人工创建的弦配置的工作一致。我们表明，振荡弦的均方速度 v̄ ' 0.500± 0.004，与 Nambu-Goto 值 1/2 一致，而网络循环的 v̄ ' 0.40 ± 0.04。我们认为，无论网络环路衰减背后的机制是什么，它都是非线性的，只能通过仔细调整初始条件来抑制，并且比引力辐射强得多。这意味着我们不能使用 Nambu-Goto 模型来导出对场论弦张力的稳健约束。我们主张将不确定性参数化为 Nambu-Goto 类环路在引力辐射下幸存下来的分数 fNG。创建的 31 个大型网络循环中没有一个存活时间超过其初始长度的 0.25，因此可以在 95% 置信水平下估计 fNG < 0.1。如果最近报道的 NANOgrav 信号是由宇宙弦引起的，则 fNG 必须大于 10−3，以免违反宇宙微波背景的界限。
We study the decay of cosmic string loops in the Abelian-Higgs model. We confirm earlier results that loops formed by intersections of infinite strings formed from random-field initial conditions disappear quickly, with lifetime proportional to their initial rest-frame length `init. We study a population with `init up to 6000 inverse mass units, and measure the proportionality constant to be 0.14± 0.04, independently of the initial lengths. We propose a new method to construct oscillating non-self intersecting loops from initially stationary strings, and show that by contrast these loops have lifetimes scaling approximately as `init, in line with previous works on artificially created string configurations. We show that the oscillating strings have mean-square velocity v̄ ' 0.500± 0.004, consistent with the Nambu-Goto value of 1/2, while the network loops have v̄ ' 0.40 ± 0.04. We argue that whatever the mechanism behind the network loop decay is, it is non-linear, can only be suppressed by careful tuning of initial conditions, and is much stronger than gravitational radiation. An implication is that one cannot use the Nambu-Goto model to derive robust constraints on the tension of field theory strings. We advocate parametrising the uncertainty as the fraction fNG of Nambu-Goto-like loops surviving to radiate gravitationally. None of the 31 large network loops created survived longer than 0.25 of their initial length, so one can estimate that fNG < 0.1 at 95% confidence level. If the recently reported NANOgrav signal is due to cosmic strings, fNG must be greater than 10−3 in order not to violate bounds from the Cosmic Microwave Background.