Abelian-Higgs宇宙弦网络的多信使约束
Multi-messenger constraints on Abelian-Higgs cosmic string networks
AI总结：
本文参数化同时产生粒子与引力波的Abelian-Higgs宇宙弦网络，结合NANOGrav、CMB、DGRB及暗物质约束给出多信使限制。
摘要：
Abelian-Higgs（AH）模型中的Nielsen-Olesen涡旋是规范场论中宇宙弦最简单的实现。大规模数值解表明，由随机初始条件产生的AH弦网络，其主导衰变通道是经典场辐射。然而，这些结果也表明，在特殊初始条件下，可以产生经典场辐射受到抑制的弦环，其行为类似于Nambu-Goto（NG）弦，主导衰变通道为引力辐射。这表明宇宙弦通常既是高能粒子源，也是引力波源。本文采用一种允许粒子和引力波同时产生的AH弦网络简单参数化。结合一个关于类NG弦环分布的具体模型，这为该模型的“多信使”研究奠定了基础。我们发现，为了解释NANOGrav对可能的引力波背景的探测，同时满足模拟对类NG弦环产生的约束以及宇宙微波背景的界限，以Planck单位表示的AH弦张力Gμ和类NG弦环比例f_NG应在95%置信度下满足Gμ f_NG^{2.6} ≳ 3.2×10^{-13}。另一方面，对于这样的弦张力，弥散伽马射线背景（DGRB）的约束表明，网络总能量的97%以上必须转化为暗物质（DM）或暗辐射。我们还考虑了由弦衰变产生的DM的湮灭截面、质量和残余丰度的联合约束。例如，对于500 GeV的DM质量，观测到的残余丰度可以由同时解释NANOGrav信号的衰变AH弦来说明。
英文摘要：
Nielsen-Olesen vortices in the Abelian-Higgs (AH) model are the simplest realisations of cosmic strings in a gauge field theory. Large-scale numerical solutions show that the dominant decay channel of a network of AH strings produced from random initial conditions is classical field radiation. However, they also show that with special initial conditions, loops of string can be created for which classical field radiation is suppressed, and which behave like Nambu-Goto (NG) strings with a dominant decay channel into gravitational radiation. This indicates that cosmic strings are generically sources of both high-energy particles and gravitational waves. Here we adopt a simple parametrisation of the AH string network allowing for both particle and gravitational wave production. With a reference to a specific model for NG-like loop distribution, this sets the basis for a ``multi-messenger'' investigation of this model. We find that, in order to explain the NANOGrav detection of a possible gravitational wave background, while satisfying the constraint on NG-like loop production from simulations and bounds from the cosmic microwave background, the tension of the AH string in Planck units $Gμ$ and the fraction of the NG-like loops $f_{\rm NG}$ should satisfy $Gμf_{\rm NG}^{2.6} \gtrsim 3.2\times 10^{-13}$ at 95$\%$ confidence. On the other hand, for such string tensions, constraints from the diffuse gamma-ray background (DGRB) indicate that more than 97$\%$ of the total network energy should be converted to dark matter (DM) or dark radiation. We also consider joint constraints on the annihilation cross-section, the mass, and the relic abundance of DM produced by decays of strings. For example, for a DM mass of 500 GeV, the observed relic abundance can be explained by decaying AH strings that also account for the NANOGrav signal.
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