Finite and infinite-dimensional symmetries of pure N=2 supergravity in D=4

We study the symmetries of pure N = 2 supergravity in D = 4. As is known, this theory reduced on one Killing vector is characterised by a non-linearly realised symmetry SU(2, 1) which is a non-split real form of SL(3, C). We consider the BPS brane solutions of the theory preserving half of the supersymmetry and the action of SU(2, 1) on them. Furthermore we provide evidence that the theory exhibits an underlying algebraic structure described by the Lorentzian Kac-Moody group SU(2, 1)(+++). This evidence arises both from the correspondence between the bosonic space-time fields of N = 2 supergravity in D = 4 and a one-parameter sigma-model based on the hyperbolic group SU(2, 1)(++), as well as from the fact that the structure of BPS brane solutions is neatly encoded in SU(2, 1)(+++). As a nice by-product of our analysis, we obtain a regular embedding of the Kac-Moody algebra su(2, 1)(+++) in e(11) based on brane physics.