Our Universe in collision with another one This question is related to the possibility that there are many other universes in the UNIVERSE,the multiverse, that were created during collisions between membranes, according to string theories. The mechanism is not needed to be discussed in any detail, unless it helps to answer the question. 
Since there is a multitude of universes, there must be non-zero probability for “our universe” to collide with another one.  
THE 2-STAGE QUESTION IS:
How can we detect by means of an experiment that our universe is in collision process with one of the many universes?
Could observations such as the accelerated expansion of our universe, or the dark flow phenomenon be an indications?
 A: One possible way* a collision with another universe could affect ours is by producing a large-scale anisotropy in the universe as a whole. Researchers recently found a "cold spot" in the cosmic microwave background that has not yet been explained by processes known to physics within the universe (https://arxiv.org/pdf/1704.03814.pdf), meaning that it could be the result of such an event (in the sense of "there's a nonzero, but still very small, probability that this is the correct explanation").
I have not heard of any arguments** linking the accelerated expansion of the universe to collisions with other universes.
Even the existence of the dark flow is still hotly debated; for example, observations from the ESA's Planck satellite are not consistent with dark flow observations made earlier (https://arxiv.org/abs/1303.5090). If dark flow exists, NASA's Goddard Space Flight Center's Alexander Kashlinsky says that we don't have enough information to count it as evidence of another universe, let alone specifically a collision (https://www.seeker.com/mysterious-dark-flow-may-be-tug-of-other-universe-1765035964.html).
*There are probably many other ways, but I've only read a small fraction of the cosmology theory papers out there, and I've understood an even smaller fraction. Nearly every question that starts with "Could" or "Can" in physics has the answer, "Yes, in some theorist's version of reality," and any question starting with "How" can be answered in a myriad of ways depending on the answerer's preference.
**Again, I've only read so many cosmology papers, so the argument may indeed be out there.
A: Well, the quest is interesting. For a moment let's think of our universe in collision with other universe. If the universe is spherical in shape, it might have taken the shape of letter 8 . After this,the expansion must not be same in all direction .But if we compare this consequence with what we observe,it doesn't match. As per the observation, the accelerated expansion and dark flow phenomenon  is same in all direction. Hence it can't be taken as indications of collision of the universe. 
