Topological Effects in Our Brane World From Extra Dimensions

The theories in which our world presents a domain wall (brane) embedded in large extra dimensions predict new types of topological defects. These defects arise due to the fact that the brane on which we live spontaneously breaks isometries of the extra space giving mass to some graviphotons. In many cases the corresponding vacuum manifold has nontrivial homotopies – this gives rise to topologically stable defects in four dimensions, such as cosmic strings and monopoles that carry gravimagnetic flux. The core structure of these defects is somewhat peculiar. Due to the fact that the translation invariance in the extra direction(s) is restored in their core, they act as “windows” to the extra dimensions. We also discuss the corresponding analog of the Alice strings. Encircling such an object one would get transported onto a parallel brane.