In the concept of a multiverse, which posits the existence of multiple universes or regions of space-time beyond our observable universe, the specific details and properties of each universe can vary. The nature of interactions between universes, if they exist, is largely speculative and not yet well understood.
In some theories of the multiverse, such as the inflationary multiverse hypothesis, it is suggested that different universes can emerge as a result of cosmic inflation, a rapid expansion of space that occurred in the early moments of our own universe. According to this idea, each universe would have its own distinct set of physical laws and properties.
In such a scenario, it is generally thought that the boundaries between different universes would be extremely difficult, if not impossible, to observe directly. The reason is that any information or signals from other universes would need to traverse the space between them, and if the laws of physics in each universe are distinct, it is unclear how such interactions would occur.
However, it's worth noting that the concept of a multiverse is still speculative, and our understanding of it is limited. There are various interpretations and theories within the framework of a multiverse, and the question of observability between universes is an area of ongoing research and exploration in theoretical physics and cosmology.