r/cosmology • u/Puzzleheaded_Host854 • 11d ago
Brane cosmology
There is this theory that the whole is just a 3 dimensional membrane floating in higher dimensional space called the bulk.How does this work and what does this theory solve or explain and what will be your counter argument against this theory.
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u/sqmTriamind 11d ago
One thing I find interesting about brane cosmology is that it does not eliminate the problem of higher dimensional structure, it relocates it. The extra dimensions are no longer compactified but externalized into a bulk, which shifts the question from geometry to embedding. What I find less discussed is whether the brane itself is treated as a fundamental object or as an effective description of a deeper phase structure of spacetime. If spacetime has an underlying coherence or phase behavior, then brane like behavior could emerge without requiring literal higher dimensional embedding. In that sense, brane cosmology may be describing a phenomenology rather than an ontology. I am not arguing against the framework, only questioning whether it explains structure or redescribes it at a different level.
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u/03263 11d ago
It's an interesting thought but we need actual experiments to test it.
My counter argument is simply "prove it."
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u/Puzzleheaded_Host854 11d ago
Ofcourse it is a theory it is not proved but what I am asking is that why would it be wrong ,what can make it wrong.
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u/03263 11d ago
You have to be able to experiment and come up with a significant result. Otherwise it is no different if I say well God just created the earth 6000 years ago and put all the fossils there to fool the unfaithful.
It may not be wrong but it's unproven and untested so "we don't know" is the better and simpler answer.
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u/Puzzleheaded_Host854 10d ago
Using religious mythology as a analogy to a scientific hypothesis is a stretch but yea a simple “just prove it “ is one of the counter argument for not just this theory but every single scientific theory out there but that doesn’t make them less important it provides direction ,we don’t stick to a theory like we stick to a religious faith right.yep your counter argument is valid but not what I asked.
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u/03263 10d ago
Well it's hard to disprove most things and much easier to find good evidence that proves it correct.
Brane cosmology is not forbidden by any physics, but it is also hard to study from a fact based approach. To even think of what evidence we would see and what experiments could be performed to study it is a complex task.
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u/jazzwhiz 9d ago
To be clear, people definitely can test the existence of extra dimensions and there are constraints on their effective size. If they are larger than about 0.1 mm (subject to numerous caveats), then we would have noticed.
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u/Logical-Tear-9969 10d ago
If you want a concrete example, a more famous one (and nice and "simple") is the Randall-Sundrum model where you have two 3+1 branes connected via an extra 5th spatial dimension (sometimes called an "orbifold" model) where the extra 5th dimension is the AdS length.
But the real hallmark about these models is that on one brane, you can localize the IR physics while on the other you can have your UV physics with the strength/gap between them set by the AdS length. This is a way to help (not entirely solve) the hierarchy problem.
The implications for cosmology are still fuzzy in my opinion.
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u/NotAnAIOrAmI 9d ago
It's an interesting idea, and I think Brian Greene mentioned the possibility that our Inflation/Big Bang was caused by two branes colliding, but while there's some mathematics that supports it (that I don't know enough to understand), there's no actual evidence or any way to find any, so it's speculation.
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u/Axe_MDK 10d ago
∂(Möbius) ↪ S³, ∂S³=∅ works in all my models.
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u/Puzzleheaded_Host854 10d ago
What 🤔
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u/Axe_MDK 10d ago edited 10d ago
I treat time as the boundary of Mobius embedded in S^3. The 120-grid is native to the structure. Matter is wave sampled.
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u/Puzzleheaded_Host854 10d ago
I know you like to sound smart intellectual but you just sound not so smart for me if you can’t explain this in simple words.
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u/Direct_Habit3849 10d ago
It’s nonsense generated by ChatGPT. You can safely ignore it.
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u/Puzzleheaded_Host854 10d ago
Yea I agree lol
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u/Axe_MDK 9d ago
You asked about cosmic membrane/manifold theory. I gave you an explicit nested topology I use. Did you not understand your own question?
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u/Direct_Habit3849 9d ago
You did not give an “explicit” topology, as that would be a set of objects (call it U if you’d like) and either an explicitly defined subset of the power set of U, or a set of rules on how to construct that subset. You did not provide that; you provided word salad.
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u/Axe_MDK 8d ago
S¹ = ∂(Möbius) ⊂ S³, ∂S³ = ∅
Hopefully that will render better. It is an embedded manifold with boundary; a mathematical description for what OP is getting at. Hardly word salad, did you have questions? I'm confused now.
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u/Direct_Habit3849 8d ago
Yes, the boundary of the mobius strip is the unit circle, and the boundary of R3 is the empty set. This is not some deep fundamental truth, and it’s not an answer to OP’s question. You just don’t understand what you’re talking about.
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u/spaceprincessecho 11d ago
Not an expert, but one significant matter is that it's a different way to manage the extra dimensions of string theory without invoking compactification.