A Self-gravitating Dirac-Born-Infeld Global Monopole

TL;DR

This paper explores the gravitational properties of a Dirac-Born-Infeld (DBI) global monopole, revealing differences from canonical monopoles in core size, effective mass, and light deflection, with implications for understanding spacetime defects.

Contribution

It extends the global monopole theory to DBI fields, providing asymptotic and numerical solutions that highlight unique gravitational effects compared to canonical monopoles.

Findings

DBI monopoles have smaller cores and larger effective mass than canonical monopoles.

The gravitational effect includes a deficit angle and negative mass at the origin.

Effective mass of DBI monopoles can be independent of false vacuum scale when the warp factor is small.

Abstract

We generalize the field theory of global monopole to Dirac-Born-Infeld(DBI) field and investigate the gravitational property of a DBI global monopole in four-dimensional spherically symmetric spacetime. The coupled equations for the metric and the DBI scalar field are solved asymptotically and numerically. It is found that, just as a canonical global monopole, the gravitational effect of DBI global monopole is equivalent to that of a deficit solid angle in the metric plus a negative mass at the origin. However, compared with a canonical global monopole, for the same false vacuum and symmetry breaking scale, a DBI global monopole has a relatively smaller core and a larger absolute value of effective mass. Thus, it can give out a larger deflect angle when the light passing by. Especially, when the scale of warp factor is small enough, the effective mass of a DBI global monopole does not depend apparently on the value of the false vacuum, which is qualitatively different from that of a canonical global monopole.