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Abstract:

We study the effective D=4, N=1 supergravity description of five-dimensional heterotic M theory in the presence of an M5 brane, and derive the Killing vectors and isometry group for the Kähler moduli-space metric. The group is found to be a non-semi-simple maximal parabolic subgroup of Sp(4,R), containing a nontrivial SL(2,R) factor. The underlying moduli space is then naturally realized as the group space Sp(4,R)/U(2), but equipped with a nonhomogeneous metric that is invariant only under that maximal parabolic group. This nonhomogeneous metric space can also be derived via field truncations and identifications performed on Sp(8,R)/U(4) with its standard homogeneous metric. In a companion paper we use these symmetries to derive new cosmological solutions from known ones. © 2005 The American Physical Society.

Abstract:

We investigate the time-dependent behaviour of brane-antibrane orbital systems, mainly concentrating on the stability of the "Branonium" configuration.

Abstract:

We study four-dimensional low energy effective actions for conifold transitions of Calabi-Yau spaces in the context of IIB supergravity. The actions are constructed by examining the mass of D3-branes wrapped on collapsing/expanding three-cycles. We then study the cosmology of the conifold transition, including consequences for moduli stabilization, taking into account the effect of the additional states which become light at the transition. We find, the degree to which the additional states are excited is essential for whether the transition is dynamically realized. © 2005 The American Physical Society.