‘Brane World Phenomenology’, bases itself on two main principles: the concept of hidden compact dimensions and the string-theoretic idea of $D_p$-branes. The simplest brane-world scenario is the so-called Arkani-Hamed—Dimopoulos—Dvali (ADD) model[@ADD], in which there are $d$ extra spatial dimensions, compactified on a $d$-torus of radius $R_c$ each way. Together with the four canonical Minkowski dimensions, this constitutes the ‘bulk’ spacetime. In this scenario the radius $R_c$ of the extra dimensions can be as large as a quarter of a millimeter[@LCP]. However, the SM fields are confined to a four-dimensional slice of spacetime, with thickness not more than $10^{-17}$ cm, which is called the ‘brane’. If the ADD model is embedded in a string-theoretic framework, the ‘brane’ is, in fact a $D_3$-brane, i.e. a 3+1 dimensional hypersurface on which the ends of open strings are confined[@Polchinksi]. However, it is not absolutely essential to embed the model in a string theory, and the word ‘brane’ or ‘wall’ is then used simply to denote the hypersurface (or thin slice) where the SM fields are confined. A crucial feature of this model is that gravity, which is a property of spacetime itself, is free to propagate in the bulk. As a result

-   Planck’s 