Stable Electroweak Strings and Nambu Monopoles Nested at Inert-Higgs Interfaces

@misc{nitta2026stable,
  title = {{Stable Electroweak Strings and Nambu Monopoles Nested at Inert-Higgs Interfaces}},
  author = {Muneto Nitta},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.39173},
  eprint = {2610.39173},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.39173},
}

TY  - UNPB
TI  - Stable Electroweak Strings and Nambu Monopoles Nested at Inert-Higgs Interfaces
AU  - Muneto Nitta
PY  - 2026
DA  - 2026/10/29
PB  - arXiv
DO  - 10.48550/arxiv.2610.39173
UR  - https://arxiv.org/abs/2610.39173
AB  - Electroweak Z strings are generally unstable, and their Nambu-monopole endpoints lack topological protection in the bulk. Using degenerate inert and inert-like Higgs vacua as a solvable reference, we show that their interface supports both defects. The analytic interface carries a normalizable SU(2) relative-orientation field. Its effective theory supports locally stable unit-flux Z strings in a one-vacuum phase and fractional Z strings in a two-vacuum phase. The fractional string carries an S^2 orientation field; a Nambu monopole is a second kink between symmetry-related, equal-tension Z strings. We identify phases in which Nambu monopoles are confined or deconfined within the interface: in the confined phase, their Z flux is concentrated into fractional strings, whereas in the deconfined phase, the monopole becomes a vortex within the interface and its Z flux spreads radially through the interface. The electromagnetic magnetic field extends outside the interface in both phases. We determine analytic string profiles, effective-theory stability regions, and the unchanged electromagnetic magnetic charge across this confinement transition.
ER  -