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Let us suppose that we have a system of multiverses, each universe within the multiverse existing as a higher-dimensional hyperspherical bubble within the yet higher-dimensional multiverse.

There have been theories about ekpyrotic universes, where M-branes collide, each collision triggering a new big-bang. However, I am considering something with much lower energy... where the two universes sit very close together, and vibrations of the universes' structures as a result of the energy of their contact leads to them meeting and parting at semi-regular intervals, until they either merge permanently or pass out of range of each other.

The universes in question would be similar to - or would be - our own, enough so that humans could exist in both, though with very slightly different physical constants. Each universe would have its own time dimension, running at a slightly different rate to that of its neighbor's, seperate to a multiversal time dimension which governs the movement of universes within the multiverse.

What I had in mind was something like the following: Billions of years ago, a previous universe was restarted in a violent ekpyrotic event, splitting into two universes. Then, a few billion years ago, the two new universes collided relatively gently, like two soap bubbles touching. The reverberations within the two universes led to the contact breaking and resuming over the subsequent inter-universal time many times, at a decreasing interval and violence, until the two universes reach a stasis with a small volume of intersection, ar least until the gravitational influence of another passing universe pulls the two apart again.

With the two universes in contact, wormhole-mouths would open between the two at the contact points or the two universe's matter would cross over. Because the universes are wrinkled, contact would not be uniform over a very large area, but would occur over a number of relatively small points over the general area of the greater point of contact. Because the areas of the universes have been in gravitic proximity for a great deal of time, matter tends to accumulate in the corresponding parts of the other, so there are parallel stars and planets in the zone of contact. Because of relative frames of reference, the curvature of spacetime would remain relatively constant with respect to the nearest, largest mass, though they may drift slowly over time.

Because the universes each have their own time dimensions, time would pass in each at different rates, though at a fixed ratio - while in contact. When not in contact, movement of the universes relative to one-another would result in the contact zones being slightly different during subsequent collisions, both in space and time...

So to the question:

Is this a feasible way to have a reasonably believable 'Different dimensions merging into one another' scenario? Could it be improved?

Monty Wild
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    Sepehri et al. 2016 appears to describe a scenario similar to the one you're interested in, but I understand essentially none of it. – HDE 226868 Jun 01 '20 at 14:27
  • @HDE226868 Sepheri et al. 2016 seems to propose a model where our own universe would naturally oscillate between inflation and contraction, with a big-bang event every 33 billion years... but the math is beyond me. What I am suggesting is two different universes coming together due to some force such as gravity, and the energy of their impact upon each other causing their n-spherical shape to oscillate so that the collision isn't instantaneous, but takes several billion years to reduce in energy and interval until the two universes are touching and are at rest relative to one another. – Monty Wild Jun 01 '20 at 15:33
  • I brought it up inasmuch as it described wormholes forming between two branes after a collision, lending support to the use of wormholes in your scenario. – HDE 226868 Jun 01 '20 at 16:37
  • The description of the "time dimensions" is very confusing. Are they actual independent dimensions? What's the number of dimensions and signature of each universe's spacetime manifold and of the total spacetime they are embedded in? – pregunton Jun 02 '20 at 10:13
  • @pregunton, The universes in question are our own, and another very similar to our own... However each has a seperate time dimension, so when jammed together, may not necessarily be at the same time in both, different amounts of time may have passed since the last collision overlap. – Monty Wild Jun 02 '20 at 18:24
  • @MontyWild I think I get what you're trying to do, but that setup does not work in a physical sense. You say that there is a "multiversal time" allowing the universes to move, and that each universe has another different internal time dimension. This is a two-time theory, which is known to be causally inconsistent due to the presence of CTCs. There is also a problem of interpretation: the collisions would occur only as seen from "multiversal time", whereas inside observers which only feel that universe's "internal time" would be actually unable to perceive the collision. – pregunton Jun 02 '20 at 19:28
  • @MontyWild (See also this related question). If you just want different relative time rates, ordinary general relativity can already achieve that with a single time dimension (this is what the movie Interstellar did!). – pregunton Jun 02 '20 at 19:29

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I suspect that it might just be possible. There are so many if's, but's and unknown's that almost anything is possible. But the interaction between the universes time and space dimensions would be interesting and fearfully complex to sort out mathematically.

One point to be wary of however is dimensionality. collisions with another universe from another higher dimension would not occur at the "edge" of the universe they would occur throughout it and if "wrinkled" at multiple points. Think a wrinkly sphere intersecting a 2D plane the intersection point would be a lot of wiggly lines.

In 4D that would probably morph into irregular 3D shells possibly nested and asorted blobs of enormous dimensions.

Slarty
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  • To use a metaphor, I'm effectively looking for a straw strong enough to grasp without it crumbling immediately, or having to fall back on magic. As I see it, the universes would be 3+1-D surfaces on a 5-sphere, and the contact would be surface-only (in 5-D)... meaning that both space and time would be merged over a volume perhaps the size of a galaxy and an interval of 100,000 years, give or take a bit. – Monty Wild Jun 01 '20 at 15:41