Branes and Brane Worlds in M-Theory

A new class of warped Anti-de Sitter solutions is found, arising as the near-horizon region of various semi-localized brane intersections. The dual gauge theories of AdS in warped spacetimes have reduced supersymmetry, which is pertinent to the study of viable supersymmetric extensions of the Standard Model. In addition, various supergravity solutions are probed via the absorption of various fields. In particular, we calculate exact absorption probabilities which provide finite-energy probes of supergravity solutions away from the conformal limit. Lastly, we discuss how brane world scenarios may arise from the near-horizon region of various p-brane configurations. Motivated by the dual non-commutative gauge theory, it is shown how a background B field mimics a negative four-dimensional cosmological constant, such that in both cases there is a massive four-dimensional graviton.