Brane Realization of Nambu Monopoles and Electroweak Strings

Understand

In the standard model, the electroweak Z-string can end on a Nambu monopole, whose mass is calculated to be 689 GeV from the current precise experimental data assuming the new particle with mass 125 GeV to be the Higgs boson.

• We study an extension of the standard model with additional singlet and triplet Higgs fields in the framework of N=1 supersymmetric field theory by using a D-brane configuration in type IIA string theory.
• We construct a D-brane configuration describing the electroweak symmetry breaking, and find a single D2-brane configuration describing a Z-string and a Nambu monopole attached by a Z-string in the standard model without an adjoint Higgs field.
• We further find a single D2-brane configuration describing a composite of a 't Hooft-Polyakov monopole and a Nambu monopole attached by a Z-string in an extended standard model with an adjoint Higgs field.