How do spherical black holes grow monopole hair?

Creators: Hegade K. R., Abhishek; Most, Elias R.; Noronha, Jorge; Witek, Helvi; Yunes, Nicolás

Abstract

Black holes in certain modified gravity theories that contain a scalar field coupled to curvature invariants are known to possess (monopole) scalar hair while non-black-hole spacetimes (like neutron stars) do not. Therefore, as a neutron star collapses to a black hole, scalar hair must grow until it settles to the stationary black hole solution with (monopole) hair. In this paper, we study this process in detail and show that the growth of scalar hair is tied to the appearance and growth of the event horizon (before an apparent horizon forms), which forces scalar modes that would otherwise (in the future) become divergent to be radiated away. We prove this result rigorously in general first for a large class of modified theories, and then we exemplify the results by studying the temporal evolution of the scalar field in scalar Gauss-Bonnet gravity in two backgrounds: (i) a collapsing Oppenheimer-Snyder background, and (ii) a collapsing neutron star background. In case (i), we find an exact scalar field solution analytically, while in case (ii) we solve for the temporal evolution of the scalar field numerically, with both cases supporting the conclusion presented above. Our results suggest that the emission of a burst of scalar field radiation is a necessary condition for black hole formation in a large class of modified theories of gravity.

Additional Information

© 2022 American Physical Society. The authors thank Professors Robert Wald, Piotr Chruściel, and Frans Pretorius for helpful discussions and comments. A. H. and N. Y. acknowledge support from the Simons Foundation through Grant No. 896696. E. R. M. acknowledges support from postdoctoral fellowships at the Princeton Center for Theoretical Science, the Princeton Gravity Initiative, and the Institute for Advanced Study. J. N. is partially supported by the U.S. Department of Energy, Office of Science, Office for Nuclear Physics under Award No. DE-SC0021301. H. W. acknowledges financial support provided by NSF Grants No. OAC-2004879 and No. PHY-2110416, and Royal Society (UK) Research Grant No. RGF\R1\180073. This work used the Blue Waters sustained-petascale computing project which is supported by National Science Foundation Grants No. OCI-0725070 and No. ACI-1238993, the State of Illinois and the National Geospatial Intelligence Agency. Blue Waters is a joint effort of the University of Illinois at Urbana-Champaign and its National Center for Supercomputing Applications. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant No. ACI-1548562. The authors acknowledge the Texas Advanced Computing Center (TACC) at The University of Texas at Austin for providing HPC resources that have contributed to the research results reported within this paper, under Leadership Resource Allocation Grant No. AT21006. Part of the simulations presented in this article were performed on computational resources managed and supported by Princeton Research Computing, a consortium of groups including the Princeton Institute for Computational Science and Engineering (PICSciE) and the Office of Information Technology's High Performance Computing Center and Visualization Laboratory at Princeton University.

Attached Files

Published - PhysRevD.105.064041.pdf

Files

PhysRevD.105.064041.pdf

Files (792.0 kB)

Name	Size	Download all
PhysRevD.105.064041.pdf md5:38ceecde6f4585fef6875a5709eb7405	792.0 kB	Preview Download

Additional details

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes