Topological defects in the Georgi-Machacek model
Topological defects in the Georgi-Machacek model
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DOI：
10.1103/physrevd.97.115010
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发表时间：
2018-01
影响因子：
5
通讯作者：
C. Chatterjee;M. Kurachi;M. Nitta
中科院分区：
文献类型：
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作者：
C. Chatterjee;M. Kurachi;M. Nitta
我们研究了Georgi-Machacek模型在分层对称破缺下的拓扑缺陷，其中额外的三重态在二重态之前获得真空期望值。在这个模型中，我们发现了一种拓扑稳定的非阿贝尔域壁和非阿贝尔通量管(涡)的可能性。在守恒对称性变为严格的消失规范耦合的极限下，涡旋的存在自发地破坏了守恒对称性，产生了位于涡旋周围的与非阿贝尔通量相对应的$S^2$Nambu-Goldstone(NG)模。涡旋因这些自由度而不断退化，因此称为非阿贝尔涡旋。通过考虑$U(1){\rM Y}$规范耦合，守恒对称性被明显打破，NG模被解除，所有非阿贝尔涡都落在一个拓扑稳定的$Z$弦上。这与SM中的$Z$-弦是非拓扑性的并且在真实参数区域内不稳定的SM形成对比。非阿贝尔结构域壁也破坏了守护对称性，并伴随着局域的$S^2$NG模。最后，我们讨论了以通量管为边界的磁通壁解的存在性，其中$S^2$NG模匹配。磁区壁可以通过创建一个被通量管环包围的空穴来进行量子力学衰变，并且在宇宙中是安全的。由不稳定的磁区壁产生的引力波可能会被未来的实验探测到
We study topological defects in the Georgi-Machacek model in a hierarchical symmetry breaking in which extra triplets acquire vacuum expectation values before the doublet. We find a possibility of topologically stable non-Abelian domain walls and non-Abelian flux tubes (vortices) in this model. In the limit of the vanishing $U(1)_{\rm Y}$ gauge coupling in which the custodial symmetry becomes exact, the presence of a vortex spontaneously breaks the custodial symmetry, giving rise to $S^2$ Nambu-Goldstone (NG) modes localized around the vortex corresponding to non-Abelian fluxes. Vortices are continuously degenerated by these degrees of freedom, thereby called non-Abelian. By taking into account the $U(1)_{\rm Y}$ gauge coupling, the custodial symmetry is explicitly broken, the NG modes are lifted, and all non-Abelian vortices fall into a topologically stable $Z$-string. This is in contrast to the SM in which $Z$-strings are non-topological and are unstable in the realistic parameter region.Non-Abelian domain walls also break the custodial symmetry and are accompanied by localized $S^2$ NG modes. Finally, we discuss the existence of domain wall solutions bounded by flux tubes, where their $S^2$ NG modes match. The domain walls may quantum mechanically decay by creating a hole bounded by a flux tube loop, and would be cosmologically safe. Gravitational waves produced from unstable domain walls could be detected by future experiments