近日，美国纽约大学的Xucheng Gan与德国电子同步加速器DESY的Di Liu合作并取得一项新进展。经过不懈努力，他们成功构造宇宙可变动力学混合模型。相关研究成果已于2023年11月7日在国际知名学术期刊《高能物理杂志》上发表。
据悉，门户作为连接不可见与可见区域的通道，被认为是对黑暗世界存在的一种最直观的解释。然而，早期通过门户生成的暗物质在后期受到极为严格的限制和约束。
为了缓解这种紧张关系，研究人员构建了一种随超轻CP-偶数标量宇宙学演化而变化的标量控制动力学混合模型。为实现这一目标并消除恒定的混合，他们将超轻标量（范围在10−33eV ? m0 ? eV之间）与重双电荷信使进行耦合，并在暗电荷共轭下施加Z2对称。通过这种变混合机制，当标量偏离原点时，keV-MeV暗光子暗物质通过早期冻结产生，并能在标量进行阻尼振荡时动态设置动力学混合，从而避免了后期的排斥效应。
此外，研究人员还发现，标量-光子耦合从基础物理中涌现出来，它改变了宇宙学的历史，并为实验提供了基于精细结构常数变化和等效原理违反的目标。为确保标量的自然性，研究人员将最小模型嵌入到ZN保护模型中，离散地重构了破缺位移对称性。当N约为10时，标量的质量量子修正得以抑制在10-33eV以下。
附：英文原文
Title: Cosmologically varying kinetic mixing
Author: Gan, Xucheng, Liu, Di
Issue&Volume: 2023-11-07
Abstract: The portal connecting the invisible and visible sectors is one of the most natural explanations of the dark world. However, the early-time dark matter production via the portal faces extremely stringent late-time constraints. To solve such tension, we construct the scalar-controlled kinetic mixing varying with the ultralight CP-even scalar’s cosmological evolution. To realize this and eliminate the constant mixing, we couple the ultralight scalar within 10−33eV ? m0 ? eV with the heavy doubly charged messengers and impose the Z2 symmetry under the dark charge conjugation. Via the varying mixing, the keV – MeV dark photon dark matter is produced through the early-time freeze-in when the scalar is misaligned from the origin and free from the late-time exclusions when the scalar does the damped oscillation and dynamically sets the kinetic mixing. We also find that the scalar-photon coupling emerges from the underlying physics, which changes the cosmological history and provides the experimental targets based on the fine-structure constant variation and the equivalence principle violation. To ensure the scalar naturalness, we discretely re-establish the broken shift symmetry by embedding the minimal model into the ZN-protected model. When N ~ 10, the scalar’s mass quantum correction can be suppressed much below 10-33eV.
DOI: 10.1007/JHEP11(2023)031
Source: https://link.springer.com/article/10.1007/JHEP11(2023)031