Extremal Kerr–Newman black holes with extremely short charged scalar hair
The recently proved ‘no short hair’ theorem asserts that, if a spherically-symmetric static black hole has hair, then this hair (the external fields) must extend beyond the null circular geodesic (the “photonsphere”) of the corresponding black-hole spacetime: rfield>rnull. In this paper we provid...
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| Format: | Article |
| Language: | English |
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Elsevier
2015-12-01
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| Series: | Physics Letters B |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S0370269315007984 |
| _version_ | 1819230195947667456 |
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| author | Shahar Hod |
| author_facet | Shahar Hod |
| author_sort | Shahar Hod |
| collection | DOAJ |
| description | The recently proved ‘no short hair’ theorem asserts that, if a spherically-symmetric static black hole has hair, then this hair (the external fields) must extend beyond the null circular geodesic (the “photonsphere”) of the corresponding black-hole spacetime: rfield>rnull. In this paper we provide compelling evidence that the bound can be violated by non-spherically symmetric hairy black-hole configurations. To that end, we analytically explore the physical properties of cloudy Kerr–Newman black-hole spacetimes – charged rotating black holes which support linearized stationary charged scalar configurations in their exterior regions. In particular, for given parameters {M,Q,J} of the central black hole, we find the dimensionless ratio q/μ of the field parameters which minimizes the effective lengths (radii) of the exterior stationary charged scalar configurations (here {M,Q,J} are respectively the mass, charge, and angular momentum of the black hole, and {μ,q} are respectively the mass and charge coupling constant of the linearized scalar field). This allows us to prove explicitly that (non-spherically symmetric non-static) composed Kerr–Newman-charged-scalar-field configurations can violate the no-short-hair lower bound. In particular, it is shown that extremely compact stationary charged scalar ‘clouds’, made of linearized charged massive scalar fields with the property rfield→rH, can be supported in the exterior spacetime regions of extremal Kerr–Newman black holes (here rfield is the peak location of the stationary scalar configuration and rH is the black-hole horizon radius). Furthermore, we prove that these remarkably compact stationary field configurations exist in the entire range s≡J/M2∈(0,1) of the dimensionless black-hole angular momentum. In particular, in the large-mass limit they are characterized by the simple dimensionless ratio q/μ=(1−2s2)/(1−s2). |
| first_indexed | 2024-12-23T11:25:13Z |
| format | Article |
| id | doaj.art-e7c7585eaaee48ee958eb70173a7451d |
| institution | Directory Open Access Journal |
| issn | 0370-2693 1873-2445 |
| language | English |
| last_indexed | 2024-12-23T11:25:13Z |
| publishDate | 2015-12-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Physics Letters B |
| spelling | doaj.art-e7c7585eaaee48ee958eb70173a7451d2022-12-21T17:48:57ZengElsevierPhysics Letters B0370-26931873-24452015-12-01751C17718310.1016/j.physletb.2015.10.039Extremal Kerr–Newman black holes with extremely short charged scalar hairShahar Hod0The Ruppin Academic Center, Emeq Hefer 40250, IsraelThe recently proved ‘no short hair’ theorem asserts that, if a spherically-symmetric static black hole has hair, then this hair (the external fields) must extend beyond the null circular geodesic (the “photonsphere”) of the corresponding black-hole spacetime: rfield>rnull. In this paper we provide compelling evidence that the bound can be violated by non-spherically symmetric hairy black-hole configurations. To that end, we analytically explore the physical properties of cloudy Kerr–Newman black-hole spacetimes – charged rotating black holes which support linearized stationary charged scalar configurations in their exterior regions. In particular, for given parameters {M,Q,J} of the central black hole, we find the dimensionless ratio q/μ of the field parameters which minimizes the effective lengths (radii) of the exterior stationary charged scalar configurations (here {M,Q,J} are respectively the mass, charge, and angular momentum of the black hole, and {μ,q} are respectively the mass and charge coupling constant of the linearized scalar field). This allows us to prove explicitly that (non-spherically symmetric non-static) composed Kerr–Newman-charged-scalar-field configurations can violate the no-short-hair lower bound. In particular, it is shown that extremely compact stationary charged scalar ‘clouds’, made of linearized charged massive scalar fields with the property rfield→rH, can be supported in the exterior spacetime regions of extremal Kerr–Newman black holes (here rfield is the peak location of the stationary scalar configuration and rH is the black-hole horizon radius). Furthermore, we prove that these remarkably compact stationary field configurations exist in the entire range s≡J/M2∈(0,1) of the dimensionless black-hole angular momentum. In particular, in the large-mass limit they are characterized by the simple dimensionless ratio q/μ=(1−2s2)/(1−s2).http://www.sciencedirect.com/science/article/pii/S0370269315007984 |
| spellingShingle | Shahar Hod Extremal Kerr–Newman black holes with extremely short charged scalar hair Physics Letters B |
| title | Extremal Kerr–Newman black holes with extremely short charged scalar hair |
| title_full | Extremal Kerr–Newman black holes with extremely short charged scalar hair |
| title_fullStr | Extremal Kerr–Newman black holes with extremely short charged scalar hair |
| title_full_unstemmed | Extremal Kerr–Newman black holes with extremely short charged scalar hair |
| title_short | Extremal Kerr–Newman black holes with extremely short charged scalar hair |
| title_sort | extremal kerr newman black holes with extremely short charged scalar hair |
| url | http://www.sciencedirect.com/science/article/pii/S0370269315007984 |
| work_keys_str_mv | AT shaharhod extremalkerrnewmanblackholeswithextremelyshortchargedscalarhair |