Inflationary scenarios from branes at angles

We describe a simple mechanism that can lead to inflation within string-basedbrane-world scenarios. The idea is to start from a supersymmetric configurationwith two parallel static Dp-branes, and slightly break the supersymmetryconditions to produce a very flat potential for the field that parametrises thedistance between the branes, i.e. the inflaton field. This breaking can beachieved in various ways: by slight relative rotations of the branes with smallangles, by considering small relative velocities between the branes, etc. Ifthe breaking parameter is sufficiently small, a large number of e-folds can beproduced within the D-brane, for small changes of the configuration in thecompactified directions. Such a process is local, i.e. it does not depend verystrongly on the compactification space nor on the initial conditions. Moreover,the breaking induces a very small velocity and acceleration, which ensures verysmall slow-roll parameters and thus an almost scale invariant spectrum ofmetric fluctuations, responsible for the observed temperature anisotropies inthe microwave background. Inflation ends as in hybrid inflation, triggered bythe negative curvature of the string tachyon potential. In this paper weelaborate on one of the simplest examples: two almost parallel D4-branes in aflat compactified space.Comment: 29 pages, 9 eps figures, using JHEP3.cls, published in JHE