论文标题
$ U（1）_ {t3r} $的$Δn_{eff} $的贡献
Contributions to $ΔN_{eff}$ from the dark photon of $U(1)_{T3R}$
论文作者
论文摘要
我们考虑对与$ u（1）_ {t3r} $测量相关的深色光子早期宇宙宇宙学的影响，这是一个对称群体，只有右撇子标准模型费米子在非私人的情况下以非凡的方式变化。我们发现，在这种情况下，宇宙学的限制比在新的$ u（1）$ gauge组的其他案例中要严重得多，因为深色光子夫妇是手性费米子。特别是，$ u（1）_ {t3r} $的深色光子总是在早期的宇宙中产生和平衡，无论量规耦合多么小，除非对称性破坏对称性量表极大。之所以发生这种情况，是因为，无论耦合如何弱，金石模式（等效地，纵向极化）都不会使。结果，即使是$ u（1）_ {t3r} $的极度轻，弱耦合的深色光子的极限，除非宇宙学的限制有效地排除，除非对称性破坏对称性量表极大。我们还讨论了在此模型中改善哈勃张力的可能性。
We consider the effect on early Universe cosmology of the dark photon associated with the gauging of $U(1)_{T3R}$, a symmetry group under which only right-handed Standard Model fermions transform non-trivially. We find that cosmological constraints on this scenario are qualitatively much more severe than on other well-studied cases of a new $U(1)$ gauge group, because the dark photon couples to chiral fermions. In particular, the dark photon of $U(1)_{T3R}$ is always produced and equilibrates in the early Universe, no matter how small the gauge coupling, unless the symmetry-breaking scale is extremely large. This occurs because, no matter how the weak the coupling, the Goldstone mode (equivalently, the longitudinal polarization) does not decouple. As a result, even the limit of an extremely light and weakly-coupled dark photon of $U(1)_{T3R}$ is effectively ruled out by cosmological constraints, unless the symmetry-breaking scale is extremely large. We also discuss the possibility of ameliorating Hubble tension in this model.
