New Directions for New Dimensions: From Strings to Neutrinos to Axions to...

In this talk, I discuss recent developments concerning the possibility of large extra spacetime dimensions. After briefly reviewing how such dimensions can lower the fundamental GUT, Planck, and string scales, I then outline how these scenarios lead to a new higher-dimensional seesaw mechanism for generating neutrino oscillations --- perhaps even without neutrino masses. I also discuss how extra dimensions lead to new mechanisms contributing to the ``invisibility'' of the QCD axion. This talk reports on work done in collaboration with Emilian Dudas and Tony Gherghetta.