Brane Worlds and M-theory

Extra dimensions are M-theory¿s most outlandish prediction. One of the main theoretical issues in theories with extra dimensions is that of determining their size - Moduli stabilization. In Brane Worlds models, the observable universe is regarded as a 3 + 1¿dimensional surface embedded in a 3 + 1 + d¿dimensional spacetime. Standard model particles and fields are trapped on the brane and only gravity is free to access the bulk. At low energies, gravity is localized at the 3+1¿dimensional brane allowing General Relativity to be recovered. At high energies, gravity leaks into the higher dimensional bulk, behaving in a truly higher dimensional theory. This book describes the main features of different extra dimensional theories of quantum gravity and sheds the light on some important aspects such as vacuum energy, moduli stabilization and gaugino condensates in the framework of five dimensional heterotic M-theory.