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According to superstring theory, there are at least 10 dimensions in the universe (M-theory actually suggests that there are 11 dimensions to spacetime; bosonic string theories suggest 26 dimensions). Or the newly formed 10 dimensional universe; being unstable, bifurcated into a 4(stable, or temporarily stable) and a 6 dimensional universe. Our sister universe, also being unstable curled into(compactified) into its calabi-Yau manifold or orbifold.
What makes these universes unstable?

1. Is it due to a lack of symmetry?
But 10 dimensional universe possessed supersymmetry.In a 10-D universe, there are a million possible ways to break symmetry(for eg. Assume a square membrane stretched from all 4 sides. There are 4 possible ways(corners) to break symmetry, and hence destabilize it) Does this implies that a supersymmetric universe of higher dimension is actually unstable?

2. Is it due to false vacuum state?
Do higher dimensional universes lie in a false vacuum state; and hence make a transit into a true vacuum state? (by producing a bubble universe in a true vacuum or collapsing into calabi-yau manifold)

If this instability is directly proportional to number of dimensions possessed by the universe, then doesn't it implies that lower(1,2 and 3) dimensional universes must be most stable?
Where am I wrong?
Was it a natural selection that our 4-D universe was chosen to be stable(or temporarily stable)?

Qmechanic
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  • Possible duplicates: https://physics.stackexchange.com/q/31882/2451 , https://physics.stackexchange.com/q/10651/2451 and links therein. – Qmechanic May 18 '17 at 06:33
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    Thus far, string/M-theory do not actually predict why we live in a 4d universe, your question is simply open in these theories. – ACuriousMind May 18 '17 at 10:39
  • @Qmechanic The attached links do not overlap with the question. The question is concerned with the reason behind "compactification" per se and not the "existence" of extra dimensions which is due to anomaly cancellation that happens only in 10 or 26. – Bastam Tajik Sep 01 '22 at 19:56
  • I'd look at the question oppositely, and pose it differently: Why don't the extra compact dimensions collapse? Of course, extra dimensions are needed for anomaly cancellation, but what is the physics that leaves the aperture open? I mean something similar to Pauli's exclusion principle that prevents degenerate fermionic states and results in something like degeneracy pressure in neutron stars and prevents the gravitational collapse of the star, perhaps there's some more direct physics at work here. @ACuriousMind – Bastam Tajik Sep 01 '22 at 20:06

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