Some versions of string theory, an all - encompassing theory of particle physics, suggest that our three - dimensional universe could exist within a four - dimensional sheet
called a brane.
We might be living on an object
called a brane inside a multidimensional universe.
Not exact matches
But a putative particle
called the sterile neutrino, which interacts with other particles only through gravity, would be able to travel in and out of the
brane, taking shortcuts through the extra dimensions.