T. J. Ott

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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 consider piecewise deterministic Markov processes that occur as scaling limits of discrete-time Markov chains that describe the Transmission Control Protocol (TCP). The class of processes allows for general increase and decrease profiles. Our key observation is that stationary results for the general class follow directly from the stationary results for(More)
In this contribution we exploit the potential of belief propagation in connection with sequential superparamagnetic clustering. We first give a short overview of the methods and concepts used and show how to combine them. We finally discuss some implementation issues, problems and possible advantages in comparison with Markov chain Monte Carlo methods by(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)
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)
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)
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)