Is a toroidal black hole possible?

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Discussion Overview

The discussion explores the theoretical possibility of toroidal black holes, particularly focusing on the implications of creating a massive toroidal structure and its potential to collapse into a black hole. Participants consider various scenarios, including the effects of rotation and mass addition, as well as the nature of event horizons and the geometry of black holes in higher dimensions.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that if a solar system-sized torus is created and mass is added evenly, it could potentially become a black hole, questioning the nature of the event horizon if it were toroidal.
  • Others argue that if the torus spins too fast, exceeding the Kerr limit, it would not form a black hole and would instead become unstable, breaking apart rather than settling into a toroidal shape.
  • A participant suggests that a toroidal black hole could be linked to theoretical time machines and mentions the concept of frame-dragging, although they acknowledge the need for a source to support this claim.
  • Another participant introduces the idea of hypertoroidal or hyperspherical black holes, referencing static black holes in higher dimensions and their potential shapes based on charge and rotation.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of toroidal black holes, with some supporting the idea under certain conditions while others assert that black holes will always settle into a spherical shape. The discussion remains unresolved regarding the existence and characteristics of toroidal black holes.

Contextual Notes

There are limitations in the assumptions made regarding the stability of spinning structures and the definitions of black hole shapes in higher dimensions, which are not fully explored in the discussion.

Meatbot
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What would happen if you created a solar system-sized massive torus and kept adding mass evenly until it became a black hole. Let's say it's also spinning fast enough to keep itself from collapsing. Would you get a toroidal black hole? What would happen if you were inside the toroidal event horizon? What would happen if you were at the center of the torus?
 
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If the torus is spinning too fast (above the Kerr limit) then no black hole would form, but instabilities will deviate it from axisymmetry and ultimately break it in pieces. Conversely, if a black hole forms, then it will always settle to a spherical shape. Toroidal horizons may only exist temporarily (eg as a consequence of a black hole merger).
 
Meatbot said:
What would happen if you created a solar system-sized massive torus and kept adding mass evenly until it became a black hole. Let's say it's also spinning fast enough to keep itself from collapsing. Would you get a toroidal black hole? What would happen if you were inside the toroidal event horizon? What would happen if you were at the center of the torus?
A toroidal black hole is actually one of the pieces in a theoretically possible time machine. (I really should get a source for this, as I've raised it before and ben unable to defend it.) I think it probably involves frame-dragging.
 
How about a hypertoroidal of hyperspherical black hole?
 
Meatbot said:
How about a hypertoroidal of hyperspherical black hole?

I believe static black holes in N dimensions (eg, if string theory is true, etc) must be hyperspherical as in the Schwarzschild-Tangherlini solution, however if the black hole is charged or rotates the shape is not unique.
 

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