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G. Lopes Cardoso

Publications and source records attributed to G. Lopes Cardoso.

5 recordsLinked to original sources
arXiv1997

Quantum N = 2 Supersymmetric Black Holes in the S-T Model

We consider axion-free quantum corrected black hole solutions in the context of the heterotic S-T model with half the N=2, D=4 supersymmetries unbroken. We express the perturbatively corrected entropy in terms of the electric and magnetic charges in such a way, that target-space duality invariance is manifest. We also discuss the microscopic origin of particular quantum black hole configurations. We propose a microscopic interpretation in terms of a gas of closed membranes for the instanton corrections to the entropy.

hep-th↗
arXiv1996

Classical and quantum N=2 supersymmetric black holes

We use heterotic/type-II prepotentials to study quantum/classical black holes with half the $N=2, D=4$ supersymmetries unbroken. We show that, in the case of heterotic string compactifications, the perturbatively corrected entropy formula is given by the tree-level entropy formula with the tree-level coupling constant replaced by the perturbative coupling constant. In the case of type-II compactifications, we display a new entropy/area formula associated with axion-free black-hole solutions, which depends on the electric and magnetic charges as well as on certain topological data of Calabi--Yau three-folds, namely the intersection numbers, the second Chern class and the Euler number of the three-fold. We show that, for both heterotic and type-II theories, there is the possibility to relax the usual requirement of the non-vanishing of some of the charges and still have a finite entropy.

hep-th↗
arXiv1994

Moduli Spaces and Target Space Duality Symmetries in $(0,2)\; Z_N$ Orbifold Theories with Continuous Wilson Lines

We present the coset structure of the untwisted moduli space of heterotic $(0,2) \; Z_N$ orbifold compactifications with continuous Wilson lines. For the cases where the internal 6-torus $T_6$ is given by the direct sum $T_4 \oplus T_2$, we explicitly construct the Kähler potentials associated with the underlying 2-torus $T_2$. We then discuss the transformation properties of these Kähler potentials under target space modular symmetries. For the case where the $Z_N$ twist possesses eigenvalues of $-1$, we find that holomorphic terms occur in the Kähler potential describing the mixing of complex Wilson moduli. As a consequence, the associated $T$ and $U$ moduli are also shown to mix under target space modular transformations.

hep-th↗