Monopoles in NBI-Higgs theory and Born-Infeld collapse

TL;DR

This paper investigates the behavior of magnetic monopoles in non-Abelian Born-Infeld-Higgs theory, revealing a collapse transition akin to gravitational collapse, and explores excited monopole states and their properties.

Contribution

It provides a detailed analysis of monopole solutions in NBI-Higgs theory, including the transition from regular to singular monopoles and the properties of excited states.

Findings

Existence of regular monopoles for eta > eta_{cr}

Transition to pointlike monopoles resembles gravitational collapse

Presence of excited monopole states with increasing node number

Abstract

Regular magnetic monopoles in the non-Abelian Born-Infeld-Higgs theory are known to exist in the region of the field strength parameter $\beta>\beta_{{\rm cr}}$, bounded from below. Beyond this region, only pointlike (embedded abelian) monopoles exist, and we show that the transition from the regular to singular structure is reminiscent of gravitational collapse. Near the threshold behavior is characterized by the rapidly increasing negative pressure, which typically arises in the high density NBI matter. Another feature, shared both the NBI and gravitating monopoles, is the existence of excited states, which can be thought of as bound states of monopoles and sphalerons. These are labeled by the number $N$ of nodes of the Yang-Mills function. Their masses are greater than the mass of the ground state monopole, and they are expected to be unstable. The sequence of masses $M_N$ rapidly converges to the mass of the embedded Abelian solution with constant Higgs. The ratio of the sphaleron size to that of the monopole grows with decreasing $\beta$, and, at the same time, both fall down until the solutions cease to exist, again exhibiting collapse to the pointlike monopole. The results are presented and compared both for the ordinary and the symmetrized trace NBI actions.