标题： 超冷暗标量相变对NANOGrav数据的解释 显示英文标题

标题： Supercooled Dark Scalar Phase Transitions explanation of NANOGrav data

摘要： 在nHz频率范围内的随机引力波背景（SGWB）的证据将为宇宙提供一个新的窗口。一种首选的解释是基于100 MeV-GeV尺度上的超冷却一阶相变。在本文中，我们探讨从粒子物理模型到引力波产生的可行性。我们采用一种最小的暗区模型，引入最少的必要成分，即一个新的U(1)规范群和一个动态打破对称性的暗标量。超冷却在分析中带来了挑战，这使得这种解释的可行性受到质疑：我们对此进行了研究，并超越了之前的研究，仔细考虑了真空主导阶段的影响，并明确跟踪了相变从开始到完成的过程。我们发现，所提出的模型可以成功地产生观测到的PTA SGWB信号。强烈的超冷却在新的规范耦合和标量四次方耦合之间建立了相关性，导致规范玻色子（更重的）和暗标量之间存在显著的层次结构。最终，从SGWB观测中获得的相变信息可以为早期宇宙的微观物理提供直接探测，并用于指导实验室中暗区的未来搜索。 显示英文摘要

摘要： The evidence of a Stochastic Gravitational Wave Background (SGWB) in the nHz frequency range is posed to open a new window on the Universe. A preferred explanation relies on a supercooled first order phase transition at the 100 MeV - GeV scale. In this article, we address the feasibility going from the particle physics model to the production of the gravitational waves. We take a minimal approach for the dark sector model introducing the fewest ingredients required, namely a new U(1) gauge group and a dark scalar that dynamically breaks the symmetry. Supercooling poses challenges in the analysis that put under question the feasibility of this explanation: we address them, going beyond previous studies by carefully considering the effects of a vacuum domination phase and explicitly tracking the phase transition from its onset to its completion. We find that the proposed model can successfully give origin to the observed PTA SGWB signal. The strong supercooling imposes a correlation between the new gauge coupling and the scalar quartic one, leading to a significant hierarchy between the (heavier) gauge boson and the dark scalar. Ultimately, information on phase transitions from SGWB observations could provide a direct probe of the microphysics of the Early Universe and be used to guide future searches of dark sector in laboratories.