In physics, Randall–Sundrum models (RS) (also called 5-dimensional warped geometry theory) are models that describe the world in terms of a warped-geometry higher-dimensional universe, or more concretely as a 5-dimensional anti-de Sitter space where the elementary particles (except the graviton) are localized on a (3 + 1)-dimensional brane or branes.
Such models require two fine tunings; one for the value of the bulk cosmological constant and the other for the brane tensions.
The first of the two models, called RS1, has a finite size for the extra dimension with two branes, one at each end.
It involves a finite five-dimensional bulk that is extremely warped and contains two branes: the Planckbrane (where gravity is a relatively strong force; also called "Gravitybrane") and the Tevbrane (our home with the Standard Model particles; also called "Weakbrane").
This warping, or red-shifting, generates a large ratio of energy scales, so that the natural energy scale at one end of the extra dimension is much larger than at the other end: where k is some constant, and η has "−+++" metric signature.
In 1998/99 Merab Gogberashvili published on arXiv a number of articles on a very similar theme.
[3][4][5] He showed that if the Universe is considered as a thin shell (a mathematical synonym for "brane") expanding in 5-dimensional space, then there is a possibility to obtain one scale for particle theory corresponding to the 5-dimensional cosmological constant and Universe thickness, and thus to solve the hierarchy problem.