There is a fine distinction between the Parallel and Multi Verses.
Here it is,
At first blush it seems crazy — or at least that was my own initial reaction. When cosmologists talk about “the multiverse,” it’s a slightly poetic term. We really just mean different regions of spacetime, far away so that we can’t observe them, but nevertheless still part of what one might reasonably want to call “the universe.” In inflationary cosmology, however, these different regions can be relatively self-contained — “pocket universes,” as Alan Guth calls them. When you combine this with string theory, the emergent local laws of physics in the different pocket universes can be very different; they can have different particles, different forces, even different numbers of dimensions. So there is a good reason to think about them as separate universes, even if they’re all part of the same underlying spacetime.
The situation in quantum mechanics is superficially entirely different. Think of Schrödinger’s Cat. Quantum mechanics describes reality in terms of wave functions, which assign numbers (amplitudes) to all the various possibilities of what we can see when we make an observation. The cat is neither alive nor dead; it is in a superposition of alive + dead. At least, until we observe it. In the simplistic Copenhagen interpretation, at the moment of observation the wave function “collapses” onto one actual possibility. We see either an alive cat or a dead cat; the other possibility has simply ceased to exist. In the Many Worlds or Everett interpretation, both possibilities continue to exist, but “we” (the macroscopic observers) are split into two, one that observes a live cat and one that observes a dead one. There are now two of us, both equally real, never to come back into contact.
These two ideas sound utterly different. In the cosmological multiverse, the other universes are simply far away; in quantum mechanics, they’re right here, but in different possibility spaces (i.e. different parts of Hilbert space,”
That is to say that there are many Universes operating simultaneously with our Space Time but operating under its own Laws, including Physical Laws.
In the Parallel Universe there are number of possibilities with regard to what we perceive, as what we see is what we would like to see, that is the Reality or the real thing is altered by our Perception or even the very attempt changes the nature of the thing we would like to perceive.
Please read my post(In Astrophysics) on this where I have provided information and Video how what we see is affected by our attempt to perceive it.
This is the essential difference according to latest thoughts on the subject.
What does Hinduism say on this?
1.That there is only one Reality, Brahman, and there are many Parallel Universes for our Perception.
Ekam Sath , Vipra Bahutha Vadanthi’
Reality is One, but It is Perceived as Many by the Discerning.
Discerning is he near equivalent word for the Sanskrit term for Vipra, though it is translated as the Learned by many.
The Context in which the sentence is formed lends support to my view.
The Many are Illusory in Nature depending on the level of Ignorance one has of the Reality.
The same world, event appears different to different people, depending on one’s Disposition, Swabhava.
This applies our level as well as to others.
As much as the Reality appears different to different people in our level, there are also other levels, Multi verse where the same Reality is perceived as many by many depending on their dispositions, Swabhava.
We, at our plane of Existence ,are aware of only our Swabhava, Dispoitions not the others’ at other levels of existence.
So according to Hinduism,there are Multi verses that operate under different levels on par or at the same time(for our reference I am mentioning this).
Hence Multi verses co-exist with ours.
2.In this sense Parallel verse and the Multi verses exist simultaneously.
In the former, at our level of existence we have many possible worlds depending on our intent to perceive.
Also the Multi verse do have their Parallel verses depending on the ability of those who inhabit them to perceive.
So there are many Multiverses in each of the possible , including ours.
3.This raises some interesting possibilities.
a) If one were to go back in Time and sees himself in the past, what does it belong to?
Parallel or Multiverse?
b) Again, according to Hinduism Rebirth is certain.
Let us look some example.
I am 64 now.
I should have died at least sixty four years ago.
My children int he past birth must have cremated, buried my body and religious ceremonies should have been performed( It might nor have been performed as well).
Hinduism states that the effect of these ceremonies , like Sraddha reach the deceased.
And they should have reached me.
How does it affect my present Life?
- A New Theory of Parallel Universes is Proposed (davidreneke.com)
- Parallel Multi Universe In Hinduism Astronomy (ramanan50.wordpress.com)
- Universe Illusion A Hologram Physicists Meet Adi Sankara (ramanan50.wordpress.com)