Abstract
We construct static and spherically symmetric particlelike and black hole solutions with magnetic and/or electric charge in the Einstein-Born-Infeld-dilaton-axion system, which is a generalization of the Einstein-Maxwell-dilaton-axion (EMDA) system and of the Einstein-Born-Infeld (EBI) system. They have remarkable properties which are not seen for the corresponding solutions in the EMDA and EBI systems. If solutions do not have both magnetic and electric charge, the axion field becomes trivial. In the electrically charged case, neither extreme nor the BPS saturated solutions exist. Although we can take the zero horizon radius limit for any Born-Infeld (BI) parameter b, there is no particlelike solution. In the magnetically charged case, an extreme solution does exist for the critical BI parameter (or charge) The critical BI parameter divides the solutions qualitatively. For there exists a particlelike solution for which the dilaton field is finite everywhere, while a no particlelike solution exists and the solution in the limit becomes naked for Though there is an extreme solution, the BPS saturated solution does not exist in this case. When the solutions have both magnetic and electric charge, we obtain the nontrivial axion field which plays an important role particularly for small black holes. The thermodynamical properties and the configuration of the dilaton field approach those in the magnetically charged case in the zero horizon limit, although the gravitational mass does not. This is related to the nontrivial behavior of the axion field. We can prove that there is no inner horizon and that the global structure is the same as the Schwarzschild black hole in any charged case.
- Received 22 January 2001
DOI:https://doi.org/10.1103/PhysRevD.64.024027
©2001 American Physical Society