- #1

Onyx

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- TL;DR Summary
- Are there any metrics for intra-universe wormholes?

Are there any metrics for intra-universe wormholes?

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- Thread starter Onyx
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In summary: Obviously such an idealized solution is pointless to discuss when you're asking questions like the one in this thread--just as with other idealized solutions like a Schwarzschild black hole, which describes a black hole alone in a universe where nothing else exists, it's pointless to ask many questions that people want to ask about black holes. To make your question meaningful, we have to consider the Ellis wormhole as an approximation, where the "infinity" at large distances in any exterior region is not actually infinity, but just where the solution merges into the rest of the universe. And if we treat the Ellis wormhole that way, then the solution itself cannot tell us whether its two exterior regions are part of the same universe or different ones. Either

- #1

Onyx

- 126

- 4

- TL;DR Summary
- Are there any metrics for intra-universe wormholes?

Are there any metrics for intra-universe wormholes?

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- #2

Drakkith

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- #3

Onyx

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The most famous wormhole solution, the Ellis wormhole, describes two separate sheets with opposite signs of the radial coordinate. Hence, this is a wormhole that connects two different universes. This article implies that intra-universe metrics are more rare, and says that the Aichelburg-Schein timehole is an example. So actually I already knew that there is such a metric, but my question is what would be the simplest metric to describe one (intra)?Drakkith said:

- #4

PeterDonis

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Yes.Onyx said:The most famous wormhole solution, the Ellis wormhole, describes two separate sheets with opposite signs of the radial coordinate.

No, not necessarily. Both sheets could be part of the same universe, just in different places.Onyx said:Hence, this is a wormhole that connects two different universes.

- #5

PeterDonis

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That article is somebody's personal blog. It's not a reliable source.Onyx said:This article implies that intra-universe metrics are more rare

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berkeman

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Do you mean the blog website posted by the OP:vanhees71 said:

Onyx said:This article implies that intra-universe metrics

If so, the person's name is in the website URL and also under "Contact" there. But as Peter said, it's not a valid reference.

- #8

Onyx

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- #9

Ibix

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What Peter said in #4, guessing from your paraphrase of what was said.Onyx said:

- #10

berkeman

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Sounds like a little Physicist humor to me...Onyx said:he said that any intra-universe wormhole can be made into intra

- #11

Onyx

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Another thought: perhaps a true intra-universe wormhole metric would be one where there is an option for two points to be causally connected via the "long way" or the "short way". In the Ellis wormhole there is only the path through the wormhole.berkeman said:Sounds like a little Physicist humor to me...

- #12

PeterDonis

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Not necessarily. See my post #4.Onyx said:In the Ellis wormhole there is only the path through the wormhole.

- #13

Onyx

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But how would a traveller get from ##l## to ##-l## without passing through the throat?PeterDonis said:Not necessarily. See my post #4.

- #14

PeterDonis

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By traveling through the rest of the universe from one exterior sheet to the other.Onyx said:But how would a traveller get from ##l## to ##-l## without passing through the throat?

In an idealized Ellis wormhole, where the mathematical description is taken to be exact all the way out to infinity, the two exterior sheets are not connected, each extends to infinity separately--but in an idealized Ellis wormhole, there is nothing else in the universe anyway, in either exterior sheet, so the question of whether it's an "inter-universe" or "intra-universe" wormhole is meaningless; it's a wormhole and it's the only thing that exists.

Obviously such an idealized solution is pointless to discuss when you're asking questions like the one in this thread--just as with other idealized solutions like a Schwarzschild black hole, which describes a black hole alone in a universe where nothing else exists, it's pointless to ask many questions that people want to ask about black holes. To make your question meaningful, we have to consider the Ellis wormhole as an approximation, where the "infinity" at large distances in any exterior region is not actually infinity, but just where the solution merges into the rest of the universe. And if we treat the Ellis wormhole that way, then the solution itself cannot tell us whether its two exterior regions are part of the same universe or different ones. Either is possible.

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Onyx

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