arXiv subjects

Dieter Lust

Publications and source records attributed to Dieter Lust.

241 records · Page 14Linked to original sources

arXiv1997

Moving Moduli, Calabi-Yau Phase Transitions and Massless BPS Configurations in Type II Superstrings

In this paper we discuss compactifications of type II superstrings where the moduli of the internal Calabi-Yau space vary over four-dimensional space time. The corresponding solutions of four-dimensional N=2 supergravity are given by charged, extremal BPS black hole configurations with non-constant scalar field values. In particular we investigate the behaviour of our solutions near those points in the Calabi-Yau moduli space where some internal cycles collapse and topology change (flop transitions, conifold transitions) can take place. The singular loci in the internal space are related to special points in the uncompactified space. The phase transition can happen either at spatial infinity (for positive charges) or on spheres (with at least one negative charge). The corresponding BPS configuration has zero ADM mass and can be regarded as a domain wall that separates topologically different vacua of the theory.

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arXiv1996

On the Duality between the Heterotic String and F-Theory in 8 Dimensions

In this note we compare the moduli spaces of the heterotic string compactified on a two-torus and F-Theory compactified on an elliptic K3 surface for the case of an unbroken E8 x E8 gauge group. The explicit map relating the deformation parameters alpha and beta of the F-Theory K3 surface to the moduli T and U of the heterotic torus is found using the close relationship between the K3 discriminant and the discriminant of the Calabi-Yau-threefold X(1,1,2,8,12)[24] in the limit of a large base P1.

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arXiv1996

Perturbative Couplings and Modular Forms in N=2 String Models with a Wilson Line

We consider a class of four parameter D=4, N=2 string models, namely heterotic strings compactified on K3 times T2 together with their dual type II partners on Calabi-Yau three-folds. With the help of generalized modular forms (such as Siegel and Jacobi forms), we compute the perturbative prepotential and the perturbative Wilsonian gravitational coupling F1 for each of the models in this class. We check heterotic/type II duality for one of the models by relating the modular forms in the heterotic description to the known instanton numbers in the type II description. We comment on the relation of our results to recent proposals for closely related models.

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arXiv1996

Modular Symmetries of N=2 Black Holes

We discuss the transformation properties of classical extremal N=2 black hole solutions in S-T-U like models under S and T duality. Using invariants of (subgroups of) the triality group, which is the symmetry group of the classical BPS mass formula, the transformation properties of the moduli on the event horizon and of the entropy under these transformations become manifest. We also comment on quantum corrections and we make a conjecture for the one-loop corrected entropy.

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arXiv1996

BPS Spectra and Non--Perturbative Couplings in N=2,4 Supersymmetric String Theories

We study the BPS spectrum in $D=4, N=4$ heterotic string compactifications, with some emphasis on intermediate $N=4$ BPS states. These intermediate states, which can become short in $N=2$ compactifications, are crucial for establishing an $S-T$ exchange symmetry in $N=2$ compactifications. We discuss the implications of a possible $S-T$ exchange symmetry for the $N=2$ BPS spectrum. Then we present the exact result for the 1-loop corrections to gravitational couplings in one of the heterotic $N=2$ models recently discussed by Harvey and Moore. We conjecture this model to have an $S-T$ exchange symmetry. This exchange symmetry can then be used to evaluate non-perturbative corrections to gravitational couplings in some of the non-perturbative regions (chambers) in this particular model and also in other heterotic models.

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arXiv1994

Gaugino Condensation in the Chiral and Linear Representation of the Dilaton

String effective theories with N=1 supersymmetry in four dimensions are subject of the discussion. Gaugino condensation in the chiral representation of the dilaton is reviewed in the truncated formalism in the $U_{K}(1)$-superspace. Using the supersymmetric duality of the dilaton the same investigation is made in the linear representation of the dilaton. We show that for the simple case of one gaugino condensate the results concerning supersymmtry breaking are independent of the representation of the dilaton.

hep-th↗

arXiv1994

Some Results on (0,2) Z_N Orbifold Theories with Continuous Wilson Lines

We discuss recent results on orbifold compactifications with (0,2) world sheet supersymmetry and continuous Wilson lines, emphasizing the role of modular symmetries. (This work is a contribution to the proceedings of the joint US Polish Workshop on Physics from the Planck scale to the Electro-Weak scale, Warsaw, 21.9. - 24.9.1994)

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