This is a form of classifying universes by how much of their components they share with each other. Despite this page being ultimately about universes or universe level structures, it could potentially be applied to any verse of any level, to any cosmological structure.
Any number of universes can share parts of themselves with any number of other universes, possibly sharing different things in different ways with each other, forming very complex structures.
It is important to note that what is meant by sharing is not that the involved universes have similar or even identical items but that the shared item is actually the same one existing in all such universes.
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Dimensional Sharing[]
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This is based on the hypothesis that matter vibrates at a specific frequency and that matter vibrating at different frequencies do not interact with each other. By matter it is meant all of the fundamental particles and their derivations, which includes energy as well as the fundamental forces, although, possibly with some exceptions as seen below.
This would allow multiple groupings of matter to exist on the same place without interaction or detection. It would be possible for different planets, stars, solar systems, even galaxies and clusters to coexist on the same space, possibly even occupying exactly the same place or going through each other without colliding or even noticing them. The fundamental aspect here is that all those different sets of matter would share the same spacial and temporal dimensions. They would co-exist inside the same space-time fabric. There is no theoretical limit to how many different sets of matter can co-exist. They could be infinite, but the more interactive they are the more likely it is that they are more limited in number.
By changing the vibrating frequency of an object, creature or even energy particles it would be possible to move through or communicate with the realities existing at the other frequencies. Other explanations for how matter could co-exist are possible as well.
When some interaction exists, the extent of that interaction can be defined by how different the vibrating frequencies are or in what direction they relate. For example, matter with closer vibrating frequencies can more easily interact. Another hypothesis is that states of matter with higher vibrating frequencies can perceive states of matter with lower vibrating frequencies, with the higher vibrating states being considered less dense states and the lower vibrating being considered more dense states. Things on higher vibrating states could more easily lower their vibration temporarily to allow interaction with those more denser states. Increasing the vibration of an object though, would require much more energy than lowering it, and could even be impossible to do, depending on the physical laws governing such interactions.
Another hypothesis to explain this possibility would be to consider the vibrating frequency of matter as another dimension different from space-time. Changing the frequency would be like moving through that dimension. Although accepting this hypothesis would change the classification of this possibility as it would make it that all dimensions would no longer be shared. Instead, all except that new dimensions would be shared.
No Interaction[]
On this condition, there is no way for matter existing at different frequencies to interact with each other at all. One cannot be felt or detected from another frequency in any way.
Examples:
Weak Interaction through Gravity[]
An hypothesis is that dark matter is exactly this, normal matter that vibrates at different frequencies and, therefore, does not interact with the matter of which we are made. The gravity that can be measured from dark matter is maybe the only form of interaction possible between matter vibrating at different frequencies. Seeing as there are about 5 times as much dark matter as there is normal matter on our universe, this could possibly indicate that there are 5 other full sets of matter of the entire universe all coexisting in the same space. This assuming gravity is equally felt no matter how far the emitting and receiving frequencies are. If the strength of the felt gravity is proportional to the frequency distance, the actual quantity of additional matter present in the universe could be much larger than 5 times the normal matter. Only on the same frequency would the effects of gravity be fully felt.
Examples:
- Possibly our universe.
Weak Interaction through other means[]
Like with gravity but using any other means of interaction. Gravity is differentiated because that hypothesis better matches our observations of our own universe. This could use any of the other fundamental forces or it could be done through any other means. The only commonality here is that some type of weak or subtle interaction would be possible.
Examples:
Partial Interaction[]
This option allows for some type of more obvious interaction between the different coexisting sets of matter. Maybe this only applies to actual matter and energy is shared by all sets of matter. Maybe something else entirely. This would mean that what happens in one set of matter can more easily influence the others.
Examples:
Strong Interaction[]
With this option, it becomes relatively easy to move things between the different co-existing sets of matter. Their existence is much more obvious and they would be considered just another normal part of the universe.
Examples:
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These universes only share a part of their dimensions. This could mean they share some but not all of their dimensions or even that they share an area of a dimension only instead of sharing it fully.
The most common case for these universes is for them to share the temporal dimension and at least one spacial dimension. If they only shared the temporal dimension there is another special category for that and sharing spacial dimensions without sharing a temporal one is possible but probably extremely rare. That would mean that there would exist multiple unrelated timelines inside the same space which would be odd and entirely different from just having multiple temporal dimensions in the same way that one has multiple spacial dimensions. It would mean that every position and every item inside the shared space would move along through time in two unrelated ways simultaneously.
The shared parts of space can allow travel between the universes sharing them but that is not a requirement. It is possible that the universes mark matter originating from them with some property that makes it always return to their original universe when leaving the shared areas. This property could be similar to the vibration frequencies described above or it could even be exactly that, with each universe having its own specific frequency. But this would still leave the problem of matter original to the shared area that could potentially have the ability to enter any of the universes sharing it. Even if movement between them is not allowed, all could possibly be perceived from the shared areas.
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The universes can have all space and time dimensions in common, except one. Actually they could share all of their dimensions except any number of them. As long as they share less than all their dimensions they would fit on this category. The base case is for two universes to share both the temporal dimension and all spacial dimensions except one. Those universes could share both height and depth but have a different dimension of width for example.
Another option is that, despite sharing the same spacial dimension, in each universe it is related to the others in a different way. So, a universe could be sharing its height dimension while for the other that could correspond to its width dimension. A much stranger possibility is for a universe to share a spacial dimension that corresponds to the temporal dimension of the other or vice versa.
Examples:
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Like with the previous category but, instead of always having entire dimensions shared, it is possible that two of these universes share only a part of a dimension. This area can be as big or as small as desired, it can be most of the dimension or just a little unimportant part of it. A good way to imagine this is to imagine that a specific galaxy could exist inside two universes at the same time.
Examples:
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This is the possibility that several universes might have nothing physical in common, none of their properties or contents, all being unique and individually owned and located by each universe. Even then there is a possibility of them sharing a single spiritual world. The implications of such a state aren't exactly obvious but the basic idea is that spirits of the living creatures in all the involved universes would likely be unique entities and that all the included universes would probably have common metaphysical realms, if any, like Heaven, Hell and Purgatory.
If the Godverses are considered to be a spiritual world, they would probably be seen as being shared by all the universes and higher level verses inside their corresponding Omniverse.
Such a spirit world could also be seen as just another type of dimension though making this just a special case of the above. All that has been described above in the other categories would apply to this case in the same way.
Examples:
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This is the possibility that several universes could share some thing other than their dimensions or in addition of sharing their dimensions. An easy example is for multiple universes to share the same set of physical laws. This is not the same as them having identical laws but actually being ruled by the same specific ones. This would open the possibility for laws that governed the interaction between them being inside such set. One way to see the difference is the case where some advanced civilization or entity manages to change the laws of physics inside their universe. If such universe shared those laws with others those others would also be affected. If that universe only had identical, but not the same, laws than some other universes, then those other universes would remain unaffected.
Examples:
- A group of universes created together each one defined as having a different set of possible values for the fundamental constants. They all would be ruled by the same laws, working on each universe through slightly different base values. The fundamental constants could be seen as the coordinates or serial number of each universe in such a set.
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This is the category in which all other universes that share nothing between them are classified as.
Examples:
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Concurrency of Dimensional Sharing[]
Whenever a dimension of any type is shared between two or more universes, either fully or in part, it can be shared Concurrently or Non-concurrently. When multiple dimensions are shared, each one can be shared in a different way.
Temporal comparisons between universes requires that they either share at least one temporal dimension or that they have their temporal dimensions relate to each other through some other higher temporal dimension that is part of the medium they exist in. Without one of those it is not possible to say when an event on one such universe occurred or will occur in relation to another event on the other universe. Any event would be seen as occurring at multiple unrelated times on the other universe. No meaningful comparison can be made.
When the law of relativity applies inside universes sharing their temporal dimensions with each one, their temporal relation is also conditioned by it. The strangest possibility occurs when relativity applies to one or several of the universes sharing it but not to all or when it applies to them in different ways.
Entering a universe without any shared or related temporal dimension would not allow one to define or even understand at what temporal coordinates one is entering it. Although this could be artificially achieved through some technology that would allow for the momentary creation of a temporal relation.
Concurrent[]
Dimensions shared concurrently are those that have the same scale in all the universes they exist in. A shared temporal dimension would have time pass at the same speed in all the universes it exists in. A minute in one universe is also a minute in the other. A concurrently shared space dimension would have all its points existing at the same size or zoom level inside all the universes containing it.
Examples:
Non-concurrent[]
Non-concurrently shared dimensions still have each of their points inside a universe correspond to a specific and defined point while inside another universe but the size of such points can vary greatly. This means that, for a temporal dimension, what is a minute on one universe can be a second or an hour on another. The difference could even be much greater with one minute in one universe corresponding to a million years on another. For a space dimension this would mean that one meter on one of the universes could be a kilometer on another for the same point in space could have a much greater zoom level.
Examples: