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We analyze the perturbative stability of non-supersymmetric intersecting brane world models on tori. Besides the dilaton tadpole, a dynamical instability in the complex structure moduli space occurs at string disc level, which drives the background geometry to a degenerate limit. We show that in certain orbifold models this latter instability is absent as(More)
We study supersymmetric intersecting D6-branes wrapping 3-cycles in the Type IIA T 6 /Z Z 4 orientifold background. As a new feature, the 3-cycles in this orbifold space arise both from the untwisted and the Z Z 2 twisted sectors. We present an integral basis for the homology lattice, H 3 (M, Z Z), in terms of fractional 3-cycles, for which the intersection(More)
Intersecting branes have been the subject of an elaborate string model building for several years. After a general introduction into string theory, this work introduces in detail the toroidal and Z N-orientifolds. The picture involving D9-branes with B-fluxes is shortly reviewed, but the main discussion employs the T-dual picture of intersecting D6-branes.(More)
Non-supersymmetric brane world scenarios in string theory display perturbative instabili-ties that usually involve runaway potentials for scalar moduli fields. We investigate in the framework of intersecting brane worlds whether the leading order scalar potential for the closed string moduli allows to satisfy the slow-rolling conditions required for(More)
There is geometry in the humming of the strings. Acknowledgements The first words of thanks I extend to my thesis advisor, Alexander Sevrin, for five years of fruitful cooperation before and during the work on my Ph.D. thesis, for encouragement when the flood of string theory was overwhelming at times, for his contagious enthusiasm, fail-safe support and(More)
In this paper, globally N = 1 supersymmetric configurations of intersecting D6-branes on the Z 6 orientifold are discussed, involving also fractional branes. It turns out rather miraculously that one is led almost automatically to just one particular class of 5 stack models containing the SM gauge group, which all have the same chiral spectrum. The further(More)
Weltweit haben in den letzten 20 Jahren Wissenschaftler in Industrie und Behörden Tierversuche bei der Entwicklung und Zulassung neuer Arzneimittel kontinuierlich verringern können. Allein in Deutschland konnte die Zahl der Versuchstiere auf diesem Gebiet von 4,2 Millionen im Jahre 1977 auf 740 000 im Jahre 1996 verringert werden. Dazu haben gemeinsam die(More)