Massive and massless monopoles with non-Abelian magnetic charges.

TLDR: The massless monopoles should be understood as the duals to the massless gauge bosons that appear as the mediators of the non-Abelian forces in the perturbative sector, argued in particular in a class of Sp(2{ital N}) examples.

Abstract: We use the multimonopole moduli space as a tool for studying the properties of BPS monopoles carrying non-Abelian magnetic charges. For configurations whose total magnetic charge is purely Abelian, the moduli space for non-Abelian breaking can be obtained as a smooth limit of that for a purely Abelian breaking. As the asymptotic Higgs field is varied toward one of the special values for which the unbroken symmetry is enlarged to a non-Abelian group, some of the fundamental monopoles of unit topological charge remain massive but acquire non-Abelian magnetic charges. The BPS mass formula indicates that others should become massless in this limit. We find that these do not correspond to distinct solitons but instead manifest themselves as {open_quote}{open_quote}non-Abelian clouds{close_quote}{close_quote} surrounding the massive monopoles. The moduli space coordinates describing the position and U(1) phase of these massless monopoles are transformed into an equal number of non-Abelian global gauge orientation and gauge-invariant structure parameters characterizing the non-Abelian cloud. We illustrate this explicitly in a class of Sp(2{ital N}) examples for which the full family of monopole solutions is known. We show in detail how the unbroken symmetries of the theory are manifested as isometries of the moduli space metric. We discuss themore » connection of these results to the Montonen-Olive duality conjecture, arguing in particular that the massless monopoles should be understood as the duals to the massless gauge bosons that appear as the mediators of the non-Abelian forces in the perturbative sector. {copyright} {ital 1996 The American Physical Society.}« less