Science fiction writers like to fold space for faster than light space travel. Maybe Frank Herbert in Dune was the first to use the concept. It is attractive, clever and improbable. I shall explain why and suggest a different approach for science fiction stories.
The four dimensions of the Universe happened someplace without any dimensions- and the four dimensions coincided with expansion,. So what do you think about that? Parmenides and Heraclitus considered the spatial volume. If the number of dimensions was variable at the start then it must have had zero to start with.
Space doesn’t exist. What does exist is a unified field that unfolded in four dimensions from a compact singular condition. Space in the universe is a thin part of the energy and other forms of stuff that the Universe is made of. One can shape electric fields and gravity seems to be everywhere yet space of the Universe is also a part of the field. True nothingness is not the same as space. True nothingness that existed before the Universe and in which the Universe and its four dimensions exist probably has zero dimensions.
If the Universe might have had more or less than four dimensions (if it were designed for example) it probably would need to have appeared in a tabula rasa environment with zero dimensions. The Universe field differentiated with four basic forces today (plus unknown forces such as dark energy and dark matter perhaps) is grounded in zero dimensions. Instead of folding space or in other words folding fields with all of the problems that would follow reshaping portions of the Universe and all of the fields within portions of it, science fiction writers could simply have faster than light four dimension travelers in some way slip through to the zero-dimension/four dimension point of contact where distance does not exist; yet simultaneously does.
That paradox could be why select quantum particle and waves can convey information faster than light to entangle distant particles. At some level below the Planck length, the four dimension entangled state of mass and energy may contact the zero-dimension paradox and exchange information faster than light because there is no distance from A to B in zero dimensions. The interface of four dimensions with zero dimensions would be a quantum shortcut where everything in four dimensions has no distance apart. Exploiting the interface area would be challenging of course. To remain a four dimensional entity stepping somewhat beyond to the zero dimension ‘point’ where distance and other forces do not exist (such as gravity) might be comparable to exploiting the surface of a microscopic black hole that exists without gravity yet warps space (this is only a metaphor because space doesn’t exist- it is just field phenomena that are reshaped to a warp paradigm by gravity) so one could abridge distances down to near zero for the purpose of expediting travel time. Traveling around the Earth is faster near the poles. Consider zero dimension travel to be like the north pole (or south) that continues curvature to infinity and allows access to all locations of four dimensional spacetime without distance because of the topology.
Before the singularity existed in space-time there were no dimensions. For some reason the Universe expanded with four dimensions arising, although string theory posits smaller 'hidden' dimensions. There may be no necessity that a Universe must have four dimensions instead of ten. Some cosmologists speculate that the universe may exist on the surface or event horizon of a hyper-dimensional black hole in a Universe that actually has five or more dimensions. In order for the original empty space or void that pre-existed the Universe to allow a Universe to arise with x dimensions it need have no dimensions to start with, and the appearance of dimensions in the space-time expansion of a singularity is phenomenal. Though the Universe arises, it does so in the area or volume that has no dimensions. No dimension void is the host for all possible dimensions that might appear. If all of the dimensions that exist re-existed the Universe then they would have filled the true void unto infinity and would not allow more or less dimensions to exist. I suppose that is the basic presupposition of some who regard the singularity as expanding within a four dimensional void thereby sinking string theory.https://youtu.be/Ua4Lu0Vo42g