English
 
User Manual Privacy Policy Disclaimer Contact us
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT

Released

Journal Article

Axionic instabilities and new black hole solutions

MPS-Authors
/persons/resource/persons221938

Brito,  Richard
Astrophysical and Cosmological Relativity, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;

Locator
There are no locators available
Fulltext (public)

1811.04945.pdf
(Publisher version), 4MB

PRD.99.035006.pdf
(Publisher version), 3MB

Supplementary Material (public)
There is no public supplementary material available
Citation

Boskovic, M., Brito, R., Cardoso, V., Ikeda, T., & Witek, H. (2019). Axionic instabilities and new black hole solutions. Physical Review D, 99: 035006. doi:10.1103/PhysRevD.99.035006.


Cite as: http://hdl.handle.net/21.11116/0000-0002-973A-3
Abstract
The coupling between scalar and vector fields has a long and interesting history. Axions are one key possibility to solve the strong CP problem and axion-like particles could be one solution to the dark matter puzzle. Given the nature of the coupling, and the universality of free fall, nontrivial important effects are expected in regions where gravity is strong. Here, we show that i. A background EM field induces an axionic instability in flat space, for large enough electric fields. Conversely, a homogeneous harmonic axion field induces an instability in the Maxwell sector. When carried over to curved spacetime, this phenomena translates into generic instabilities of charged black holes (BHs). ii. In the presence of charge, BH uniqueness results are lost. We find solutions which are small deformations of the Kerr-Newman geometry and hairy stationary solutions without angular momentum, which are `dragged' by the axion. Axion fields must exist around spinning BHs if these are immersed in external magnetic fields. The axion profile can be obtained perturbatively from the electro-vacuum solution derived by Wald. iii. Ultralight axions trigger superradiant instabilities of spinning BHs and form an axionic cloud in the exterior geometry. The superradiant growth can be interrupted or suppressed through axionic or scalar couplings to EM. These couplings lead to periodic bursts of light, which occur throughout the history of energy extraction from the BH. We provide numerical and simple analytical estimates for the rates of these processes. iv. Finally, we discuss how plasma effects can affect the evolution of superradiant instabilities.