Inner and outer horizon of black hole

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Discussion Overview

The discussion revolves around the concepts of inner and outer horizons in black holes, specifically focusing on their definitions and implications. Participants explore the nature of these horizons in the context of rotating black holes and the ergosphere.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant inquires about the meaning of inner and outer horizons in black holes and what occurs between them.
  • Another participant suggests that the ergosphere is relevant to the discussion, explaining that it exists outside the event horizon and allows objects to escape, but cannot remain stationary.
  • A different participant clarifies that the outer horizon of a rotating black hole is an event horizon, while the inner horizon is identified as a Cauchy horizon.
  • A link to an external resource is provided for further illustration and description of Kerr black holes and their important surfaces.

Areas of Agreement / Disagreement

The discussion includes multiple competing views regarding the definitions and implications of inner and outer horizons, and it remains unresolved whether there is a consensus on the specifics of these concepts.

Contextual Notes

Participants have not fully explored the implications of the Cauchy horizon or the ergosphere, and there may be assumptions regarding the definitions of these terms that are not explicitly stated.

sadegh4137
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hi
some black holes are inner and outer horizon!
what's this means?
inner and outer?
what happen between them?
 
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Assuming you're talking about the ergosphere: Any black hole with nonzero angular momentum has, in addition to the event horizon, an ergosphere, ie a surface inside which (but outside the event horizon) an object cannot remain stationary but can still "escape" the black hole (an object cannot escape once it passes the event horizon). That should be a concise qualitative description, and it should actually answer all three questions you posted in the OP (on a qualitative level).
 
Last edited:
The outer horizon of a rotating black hole is an event horizon, and the inner horizon is a Cauchy horizon.
 

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