Masoud Soroush

The Non-BPS black hole attractor equation

We study the attractor mechanism for extremal non-BPS black holes with an infinite throat near horizon geometry, developing, as we do so, a physical argument as to why such a mechanism does not exist in non-extremal cases. We present a detailed derivation of the non-supersymmetric attractor equation. This equation defines the stabilization of moduli near the black hole horizon: the fixed moduli take values specified by electric and magnetic charges corresponding to the fluxes in a Calabi Yau compactification of string theory. They also define the so-called double-extremal solutions. In some examples, studied previously by Tripathy and Trivedi, we solve the equation and show that the moduli are fixed at values which may also be derived from the critical points of the black hole potential.

Hints for Off-Shell Mirror Symmetry in type II/F-theory Compactifications

Abstract We perform a Hodge theoretic study of parameter dependent families of D-branes on compact Calabi–Yau manifolds in type II and F-theory compactifications. Starting from a geometric Gauss–Manin connection for B-type branes we study the integrability and flatness conditions. The B-model geometry defines an interesting ring structure of operators. For the mirror A-model this indicates the existence of an open-string extension of the so-called A-model connection, whereas the discovered ring structure should be part of the open-string A-model quantum cohomology. We obtain predictions for genuine Ooguri–Vafa invariants for Lagrangian branes on the quintic in P 4 that pass some non-trivial consistency checks. We discuss the lift of the brane compactifications to F-theory on Calabi–Yau four-folds and the effective couplings in the effective supergravity action as determined by the N = 1 special geometry of the open–closed deformation space.

Effective Superpotentials for Compact D5-Brane Calabi-Yau Geometries

For compact Calabi-Yau geometries with D5-branes we study N = 1 effective superpotentials depending on both open- and closed-string fields. We develop methods to derive the open/closed Picard-Fuchs differential equations, which control D5-brane deformations as well as complex structure deformations of the compact Calabi-Yau space. Their solutions encode the flat open/closed coordinates and the effective superpotential. For two explicit examples of compact D5-brane Calabi-Yau hypersurface geometries we apply our techniques and express the calculated superpotentials in terms of flat open/closed coordinates. By evaluating these superpotentials at their critical points we reproduce the domain wall tensions that have recently appeared in the literature. Finally we extract orbifold disk invariants from the superpotentials, which, up to overall numerical normalizations, correspond to orbifold disk Gromov-Witten invariants in the mirror geometry.

Explicit action of E7(7) on N=8 supergravity fields

We present an explicit, exact to all orders in gravitational coupling E7(7) symmetry transformations of on-shell N=8 supergravity fields in the gauge with 70 scalars in E7(7)SU(8) coset space, the local SU(8) symmetry being fixed. The non-linear realization of E7(7) includes a field-dependent SU(8) transformation preserving the unitary gauge. We find the conserved Noether–Gaillard–Zumino current of E7(7) symmetry, the linear part of it being a chiral SU(8) symmetry. We comment on the conformal realization of the E7(7) algebra which includes a dilatation operator. We hope that these results can be useful for studies of anomalies/absence of anomalies and the UV behavior of N=8 supergravity.

Issues in Type IIA Uplifting

Moduli stabilization in the type IIA massive string theory so far was achieved only in the AdS vacua. The uplifting to dS vacua has not been performed as yet: neither the analogs of type IIB anti-D3 brane at the tip of the conifold, nor the appropriate D-terms have been identified. The hope was recently expressed that the F-term uplifting may work. We investigate this possibility in the context of a simplified version of the type IIA model developed in hep-th/0505160 and find that the F-term does not uplift the AdS vacua to dS vacua with positive CC. Thus it remains a challenging task to find phenomenologically acceptable vacua in the type IIA string theory.

Issues in IIA Uplifting

Moduli stabilization in the type IIA massive string theory so far was achieved only in the AdS vacua. The uplifting to dS vacua has not been performed as yet: neither the analogs of type IIB anti-D3 brane at the tip of the conifold, nor the appropriate D-terms have been identified. The hope was recently expressed that the F-term uplifting may work. We investigate this possibility in the context of a simplified version of the type IIA model developed in hep-th/0505160 and find that the F-term does not uplift the AdS vacua to dS vacua with positive CC. Thus it remains a challenging task to find phenomenologically acceptable vacua in the type IIA string theory.