The strong, weak, and electromagnetic interactions all have consistent, relativistic and quantum mechanical descriptions in terms of pointlike particles, but Einstein's theory of gravitation has long resisted a similar treatment, because of severe ultraviolet divergences. String theory solves these problems, but it introduces a new length scale, perhaps 16 orders of magnitude below what can be tested experimentally.
Dr. Dixon will describe recent theoretical progress in showing that a particular pointlike theory of gravity, called N=8 supergravity, might also be quantum mechanically consistent. In particular, N=8 supergravity has been shown explicitly to have no ultraviolet divergences in perturbation theory through the four-loop order. Dr. Dixon will also discuss the possible implications of these results.