Drop a charge in a neutral black hole

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Discussion Overview

The discussion centers on the implications of dropping a charged particle, specifically an electron, into a neutral black hole. Participants explore theoretical aspects related to black hole charge, electromagnetic fields, and the behavior of charges near and inside event horizons, drawing on concepts from the Reissner-Nordström solution.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the fate of an electron sent into a neutral black hole, indicating a foundational understanding of black hole theory.
  • Another participant suggests that the electromagnetic field lines outside the black hole behave as if the event horizon is a perfect conducting sheet, proposing an image charge model to visualize the interaction.
  • Some participants assert that black holes can hold a charge, implying that if enough charged matter is introduced, the black hole could acquire a net charge.
  • There is mention of an image charge at the center of the black hole that balances the charge of the infalling particle, leading to a net charge on the black hole after the particle crosses the event horizon.
  • Participants express curiosity about the lack of a similar conceptual framework for understanding the interior of the black hole, noting that discussions about the interior often rely on conjecture.

Areas of Agreement / Disagreement

Participants generally agree that black holes can hold charge and that the interaction of charges with black holes can be modeled using image charges. However, there is no consensus on the understanding of the interior dynamics of black holes, with some participants expressing uncertainty and seeking further clarification.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the behavior of charges inside the event horizon and the lack of established paradigms for understanding the interior of black holes.

TeTeC
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Hello,

What would happen if I sent an electron into a neutral black hole?

Assume basic (undergraduate) knowledge about black holes. I have studied in some details the Reissner-Nordstrom solution including maximal extension using Kruskal coordinates.

Thank you!
 
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No idea ? Even if you don't have a full answer, a qualitative argument would be interesting.
 
Outside the black hole is easier to talk about. It turns out that the electromagnetic field lines act as if the event horizon is a perfect conducting sheet. So as a charge approaches, qualitatively the fields will be like there are two image charges inside: one at the center and one which is moving outwards and will meet the infalling charge at the event horizon.

Of course there is actually not a big source of charges or anything special at the event horizon. This is just an equivalent way of working with it that scientists have found, if you restrict yourself to asking questions about the region outside of the event horizon.

I don't know if there is any similar approach to simplify visualization of what is going on inside the event horizon though. Anyone?

EDIT: Just noticed that this is being discussed in another thread as well.
https://www.physicsforums.com/showthread.php?t=409465
The keyword I was having trouble remembering is "membrane paradigm". There are links to more info in that thread, but with the name of the paradigm you can easily look up plenty of stuff yourself if you'd like.
 
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Okay, thanks Justin.
 
I'm not sure if Justin's comment is in line with this, but I do believe that BHs can hold a charge.

Drop enough charged matter in, and you've got yourself a BH with a handhold!
 
DaveC426913 said:
I'm not sure if Justin's comment is in line with this, but I do believe that BHs can hold a charge.
Yep, they can hold a charge.
In that discussion above, notice the image charge at the center is there. After the infalling charge meets the horizon, this image charge at the center will equal the charge that fell in ... leaving the black hole with a net charge.

The weird part from this is that the solution is almost already symmetric (besides some radiation, etc.) in this outside region by the time the infalling charge hits the horizon! I have trouble understanding this intuitively, and find it fascinating.

Does anyone know of a similar paradigm for discussing the interior region?
 
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JustinLevy said:
Yep, they can hold a charge.
In that discussion above, notice the image charge at the center is there. After the infalling charge meets the horizon, this image charge at the center will equal the charge that fell in ... leaving the black hole with a net charge.

The weird part from this is that the solution is almost already symmetric (besides some radiation, etc.) in this outside region by the time the infalling charge hits the horizon! I have trouble understanding this intuitively, and find it fascinating.

Does anyone know of a similar paradigm for discussing the interior region?

I know of no paradigm for discussing the interior that is not pure conjecture.
 

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