String theory and inflationary cosmology (07rit135)

Arriving Sunday, June 3 and departing Sunday June 10, 2007


James Cline (McGill University)


We would like to continue the work which we started as a team in July 2006, where we made significant progress toward understanding the challenges of finding an inflationary model which uses the motion of Dp-branes to drive inflation. Using very recent results of string theorists at Princeton, we were able to compute corrections to the superpotential which governs the motion of the branes. In previous work on this subject, these corrections were merely parametrized, rather than rigorously computed. Unfortunately, the form of the actual superpotential corrections was not what previous workers had hoped for, in their quest to find an inflation model which would satisfy current experimental data.

Our goal is to look for modifications of the theory which can satisfy these constraints. There are several strategies which we intend to investigate:

(1) modifications of the background geometry of the compact extra dimensions which would generate new corrections to the potential possibly with the desired properties;

(2) exploring the possibility of fast-roll inflation, taking advantage of the special properties of the DBI action for the D3 brane in the warped-throat geometry;

(3) computing the potential for the D3-D7 brane system, for which we laid the groundwork in our previous team research.

We believe that this is an extremely important endeavor, since string theory is the paradigm of choice for thousands of theoretical physicists, and cosmology may well provide the most direct experimental test. So far, inflation and the CMB appear to be the most likely framework for probing this theory, which is surely the most mathematically sophisticated branch of theoretical physics. It is also quite timely in that many of the most prominent string theorists in the world are presently studying problems closely related to the ones we have targeted. (For example the Princeton group has announced work in progress along these lines.) Our team worked together very effectively in the previous meeting, and we look forward to making significant further progress in this proposed sequel.