 In Type II-B string theory, which requires ten spacetime dimensions, there is a five-form field strength formula_19 that allows for three dimensional D-branes, and the near horizon geometry of a stack of D3-branes is five-dimensional Anti-de Sitter space times a five-dimensional sphere, formula_20, which is compact in five dimensions.This geometry is an important part of the AdS/CFT correspondence.Similarly, M-theory and its low energy limit of contain a 4-form field strength, that stabilizes M2 and M5 branes.