The rift dimension is a dimension between the next 2 , think of this dimension ( or for a better term density ) and the next , the creatures living in the next upper dimension , the 4th, can perceive people living in the third density but not viceversa, because the limiting factor between dimension is the fundamental frequency at which the fabric of that particular dimension is vibrating.
If you consider the electromagnetic wave composed of two fields ( the electric and magnetic field ) fluctuating pahsed out of 90 degrees to each other .If you graph them, you have two vectors orthogonal to each other. Current science stops here, but, if you combine these vectors in all possibile configurations in the 3d space, you obtain a shape composed of 2 pyramids connected to the base , like the simplest diamond shape configuration. This cell is the base cell of this density, each atom is contained inside this cell and moves from the next cell to the other in a discrete step and in a discrete time. Physics call this time the Plank time and the Plank distance. Each density has a more and more complex cell to allow atoms to exits, as far as i know this cell vibrate to the fundamental frequency of its own density, the fundamental frequency here is the 'Ohm' frequency.