Two massive and one massless Sp(4) monopole

Abstract

Starting from Nahm's equations, we explore Bogomol'nyi-Prasad-Sommerfield (BPS) magnetic monopoles in the Yang-Mills-Higgs theory of the gauge group Sp(4), which is broken to $\mathrm{SU}(2)\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1)$. There exists a family of BPS field configurations with a purely Abelian magnetic charge that describes two identical massive monopoles and one massless monopole. We construct the field configurations with axial symmetry by employing the Atiyah-Drinfeld-Hitchin-Mannin-Nahm construction and find the explicit expression of the metrics for the 12-dimensional moduli space of Nahm data and its submanifolds.