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Hacker News Hacker NewsString theory usually prefers universes that want to crunch inwards (Anti-de Sitter space). Our universe, however, is accelerating outwards (Dark Energy).
To fix this, the authors are essentially creating a force balance. They have magnetic flux pushing the universe's extra dimensions outward (like inflating a tire), and they use the Casimir effect (quantum vacuum pressure) to pull them back inward.
When you balance those two opposing pressures, you get a stable system with a tiny bit of leftover energy. That "leftover" is the Dark Energy we observe.
You start with 11 dimensions (M-theory) and roll up 6 of them to get this 5D model. It sounds abstract, but for my engineer brain, it's helpful to think of that extra 5th dimension not as a "place" you can visit, but as a hidden control loop. The forces fighting it out inside that 5th dimension are what generate the energy potential we perceive as Dark Energy in our 4D world. The authors stop at 5D here, but getting that control loop stable is the hardest part
The big observatiom here is that this balance isn't static -- it suggests Dark Energy gets weaker over time ("quintessence"). If the recent DESI data holds up, this specific string theory solution might actually fit the observational curve better than the standard model.
[0] https://ocw.mit.edu/courses/8-821-string-theory-and-holograp...
1. Inhomogeneity backreaction (Moffat 2025) Large-scale cosmic inhomogeneities such as voids and dense regions can create an effective expansion history that mimics evolving dark energy when averaged using standard homogeneous assumptions. https://arxiv.org/abs/2503.20912
2. Timescape cosmology (Wiltshire) Because cosmic voids expand faster than dense regions and dominate volume at late times, observers may infer acceleration from redshift data even if the universe is not globally accelerating. https://www.livescience.com/physics-mathematics/dark-energy/...
3. Local giant void hypothesis If the Milky Way resides inside a large underdense region, locally measured redshifts and distances can bias expansion measurements and partially explain apparent acceleration and Hubble tension. https://www.livescience.com/space/cosmology/echoes-from-the-...
4. Void universe models (LTB cosmologies) Placing the observer near the center of a large cosmic void can reproduce supernova redshift–distance relations without dark energy, though such models struggle with other cosmological constraints. https://arxiv.org/abs/0807.1443
5. Structure formation and virialisation effects The growth of cosmic structure and entropy production alters averaged expansion rates, potentially generating an apparent dark-energy-like signal without introducing a new energy component. https://www.aanda.org/articles/aa/full_html/2024/09/aa50818-...
6. Redshift drift as a discriminator Measuring how cosmological redshifts change over time can distinguish true cosmic acceleration from redshift effects caused by voids or inhomogeneous expansion. https://arxiv.org/abs/1010.0091
Things he talks about go mostly over my head. What disappointed me a little bit is that he seems to be a materialist. But that is pretty common position among physicists anyway, so not that surprising.
The string theory hype machine will never die