7/27/2019 Ring Singularity

1/3

Ring singularityFrom Wikipedia, the free encyclopedia

Ring singularity is a term used in general relativity to describe the altering gravitational singularity ofa rotating

black hole, or a Kerr black hole, so that the gravitational singularity becomes shaped like a ring.[1]

Contents

1 Description ofa ring singularity

2 Traversability and nakedness

3 The Kerr singularity as a "toy" wormhole

4 Existence ofring singularities

5 See also

6 References

Description ofa ring singularity

When a spherical non-rotating body ofa critical radius collapses under its own gravitation under general relativity,

theory suggests it will collapse to a single point. This is not the case with a rotating black hole (a Kerr black hole).

With a fluid rotating body, its distribution ofmass is not spherical (it shows an equatorial bulge), and it has angular

momentum. Since a point cannot support rotation or angular momentum in classical physics (general relativity bein

a classical theory), the minimal shape ofthe singularity that can support these properties is instead a ring with zero

thickness but non-zero radius, and this is referred to as a ring singularity or Kerr singularity.

Due to a rotating hole's rotational frame-dragging effects, spacetime in the vicinity ofthe ring will undergo curvatur

in the direction ofthe ring's motion. Effectively this means that different observers placed around a Kerr black hole

who are asked to point to the hole's apparent center ofgravity may point to different points on the ring. Falling

objects will begin to acquire angular momentum from the ringbefore they actually strike it, and the path takenby a

perpendicular light ray (initially traveling toward the ring's center) will curve in the direction ofring motionbefore

intersecting with the ring.

Traversability and nakedness

An observer crossing the event horizon ofa non-rotating (Schwarzschild) black hole cannot avoid the central

singularity, which lies in the future world line ofeverything within the horizon. Thus one cannot avoid

spaghettification by the tidal forces ofthe central singularity.

This is not necessarily true with a Kerr black hole. An observer falling into a Kerr black hole maybe able to avoid

the central singularity by making clever use ofthe inner event horizon associated with this class ofblack hole. This

makes it possible for the Kerr black hole to act as a sort ofwormhole, possibly even a traversable

wormhole[citation needed].

7/27/2019 Ring Singularity

2/3

The Kerr singularity as a "toy" wormhole

The Kerr singularity can also be used as a mathematical tool to study the wormhole "field line problem". Ifa partic

is passed through a wormhole, the continuity equations for the electric field suggest that the field lines should not b

broken. When an electrical charge passes through a wormhole, the particle's charge field lines appear to emanate

from the entry mouth and the exit mouth gains a charge density deficit due to Bernoulli's principle. (For mass, the

entry mouth gains mass density and the exit mouth gets a mass density deficit.) Since a Kerr ring singularity has the

same feature, it also allows this issue to be studied.

Existence ofring singularities

It is generally expected that since the usual collapse to a point singularity under general relativity involves arbitrarily

dense conditions, that quantum effects may become significant and prevent the singularity forming ("quantum fuzz")

Without quantum gravitational effects, there is good reason to suspect that the interior geometry ofa rotatingblack

hole is not the Kerr geometry. The inner event horizon ofthe Kerr geometry is probably not stable, due to the

infinite blue-shifting ofin falling radiation.[2] This observation was supported by the investigation ofcharged black

holes which exhibited similar "infinite blueshifting" behavior.

[3]

While much work has been done, the realisticgravitational collapse ofobjects into rotating black holes, and the resultant geometry, continues to be an active

research topic.[4][5][6][7][8]

See also

Black hole

Black hole electron

Gravitational singularity

Geon (physics)

References

1. ^ Sukys, Paul (1999). Lifting the Scientific Veil. Rowman & Littlefield. p. 533. ISBN 978-0-8476-9600-0.

2. ^ Penrose, R. (1968). de Witt, C.; Wheeler, J., eds. Battelle Rencontres. New York: W. A. Benjamin. p. 222.

3. ^ Poisson, E.; Israel, W. (1990). "Internal structure of black holes". Phys. Rev. D41 (6): 1796.

Bibcode:1990PhRvD..41.1796P (http://adsabs.harvard.edu/abs/1990PhRvD..41.1796P).

doi:10.1103/PhysRevD.41.1796 (http://dx.doi.org/10.1103%2FPhysRevD.41.1796).

4. ^ Hod, Shahar; Tsvi Piran (1998). "The Inner Structure of Black Holes". Gen. Rel. Grav. arXiv:gr-qc/9902008

(http://arxiv.org/abs/gr-qc/9902008). Bibcode:1998GReGr..30.1555H

(http://adsabs.harvard.edu/abs/1998GReGr..30.1555H). doi:10.1023/A:1026654519980

(http://dx.doi.org/10.1023%2FA%3A1026654519980).

5. ^ Ori, Amos (1999). "Oscillatory Null Singularity inside Realistic Spinning Black Holes". Physical Review Letters

83 (26): 54235426. arXiv:gr-qc/0103012 (http://arxiv.org/abs/gr-qc/0103012). Bibcode:1999PhRvL..83.5423O

(http://adsabs.harvard.edu/abs/1999PhRvL..83.5423O). doi:10.1103/PhysRevLett.83.5423

(http://dx.doi.org/10.1103%2FPhysRevLett.83.5423).

6. ^ Brady, Patrick R; Serge Droz, Sharon M Morsink (1998). "The late-time singularity inside non-spherical black

holes". Physical Review D58. arXiv:gr-qc/9805008 (http://arxiv.org/abs/gr-qc/9805008).

Bibcode:1998PhRvD..58h4034B (http://adsabs.harvard.edu/abs/1998PhRvD..58h4034B).

doi:10.1103/PhysRevD.58.084034 (http://dx.doi.org/10.1103%2FPhysRevD.58.084034).

7. ^ Novikov, Igor D. (2003). "Developments in General Relativity: Black Hole Singularity and Beyond". arXiv:gr-

7/27/2019 Ring Singularity

3/3

qc/0304052 (http://arxiv.org/abs/gr-qc/0304052) [gr-qc (http://arxiv.org/archive/gr-qc)].

8. ^ Burko, Lior M.; Amos Ori (1995-02-13). "Are physical objects necessarily burnt up by the blue sheet inside a

black hole?". Physical Review Letters74 (7): 10641066. arXiv:gr-qc/9501003 (http://arxiv.org/abs/gr-

qc/9501003). Bibcode:1995PhRvL..74.1064B (http://adsabs.harvard.edu/abs/1995PhRvL..74.1064B).

doi:10.1103/PhysRevLett.74.1064 (http://dx.doi.org/10.1103%2FPhysRevLett.74.1064). PMID 10058925

(//www.ncbi.nlm.nih.gov/pubmed/10058925).

Thorne, Kip,Black Holes and Time Warps: Einstein's Outrageous Legacy, W. W. Norton & Company; Reprint

edition, January 1, 1995, ISBN 0-393-31276-3.

Matt Visser,Lorentzian Wormholes: from Einstein to Hawking (AIP press, 1995)

Retrieved from "http://en.wikipedia.org/w/index.php?title=Ring_singularity&oldid=569840229"

Categories: Black holes Wormhole theory

This page was last modified on 23 August 2013 at 09:36.

Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply.

By using this site, you agree to the Terms ofUse and Privacy Policy.

Wikipedia is a registered trademark ofthe Wikimedia Foundation, Inc., a non-profit organization.