There have been a number of attempts to construct braneworld models in which effective 4D gravity is concentrated on a sub-hypersurface of a higher-dimensional spacetime with an infinite space transverse to the braneworld. Cut-and-paste attempts using sections of AdS spaces manage to do this, but have been criticized as not really involving an infinite transverse space, or because they do not involve natural elements of string or M theory. There have also been intimations of no-go theorems about such possibilities within string or M-theory contexts. The talk will display, however, a construction that does yield massless 4D gravity in an infinite transverse space, using a type IIA background with an NS-5 brane inclusion. This produces a mass gap between the massless 4D supergravity spectrum and the edge of the continuous massive spectrum.
The seminar is free and open to all. Seating is on a first-come, first-served basis.
