Vibration isolation system for the Stratospheric Observatory For Infrared Astronomy (SOFIA)

The Vibration Isolation System for the Stratospheric Observatory for Infrared Astronomy (SOFIA) is studied. Included are discussions of the various concepts, design goals, concerns, and the proposed configuration for the Vibration Isolation System

Fermions in the background of the sphaleron barrier

We demonstrate the level crossing phenomenon for fermions in the background field of the sphaleron barrier, by numerically determining the fermion eigenvalues along the minimal energy path from one vacuum to another. We assume that the fermions of a doublet are degenerate in mass, allowing for spherically symmetric ans\"atze for all of the fields, when the mixing angle dependence is neglected.Comment: 9 pages, latex, 4 figures appended as postscript files after \end{document}. THU-93/0

Axially Symmetric Multisphalerons in Yang-Mills-Dilaton Theory

We construct sequences of axially symmetric multisphaleron solutions in SU(2) Yang-Mills-dilaton theory. The sequences are labelled by a winding number $n>1$. For $n=1$ the known sequence of spherically symmetric sphaleron solutions is obtained. The solutions within each sequence are labelled by the number of nodes $k$ of the gauge field functions. The limiting solutions of the sequences correspond to abelian magnetic monopoles with $n$ units of charge and energy $E \propto n$.Comment: 18 pages, including 7 postscript figure

Sphalerons, Antisphalerons and Vortex Rings

We present new classical solutions of Weinberg-Salam theory in the limit of vanishing Weinberg angle. In these static axially symmetric solutions, the Higgs field vanishes either on isolated points on the symmetry axis, or on rings centered around the symmetry axis. The solutions represent systems of sphalerons, antisphalerons, and vortex rings.Comment: 8 pages, 3 figures, minor corrections include

Electroweak Sphalerons with Spin and Charge

We show that, at finite weak mixing angle the sphaleron solution of Weinberg-Salam theory can be endowed with angular momentum proportional to the electric charge. Carrying baryon number 1/2 these sphalerons with spin and charge may contribute to baryon number violating processes.Comment: 5 pages, 2 figure

Analysis of Imperfections in Practical Continuous-Variable Quantum Key Distribution

As quantum key distribution becomes a mature technology, it appears clearly that some assumptions made in the security proofs cannot be justified in practical implementations. This might open the door to possible side-channel attacks. We examine several discrepancies between theoretical models and experimental setups in the case of continuous-variable quantum key distribution. We study in particular the impact of an imperfect modulation on the security of Gaussian protocols and show that approximating the theoretical Gaussian modulation with a discrete one is sufficient in practice. We also address the issue of properly calibrating the detection setup, and in particular the value of the shot noise. Finally, we consider the influence of phase noise in the preparation stage of the protocol and argue that taking this noise into account can improve the secret key rate because this source of noise is not controlled by the eavesdropper.Comment: 4 figure

Teaching about Madrid: A Collaborative Agents-Based Distributed Learning Course

Interactive art courses require a huge amount of computational resources to be running on real time. These computational resources are even bigger if the course has been designed as a Virtual Environment with which students can interact. In this paper, we present an initiative that has been develop in a close collaboration between two Spanish Universities: Universidad Politécnica de Madrid and Universidad Rey Juan Carlos with the aim of join two previous research project: a Collaborative Awareness Model for Task-Balancing-Delivery (CAMT) in clusters and the “Teaching about Madrid” course, which provides a cultural interactive background of the capital of Spain

Gravitating Sphaleron-Antisphaleron Systems

We present new classical solutions of Einstein-Yang-Mills-Higgs theory, representing gravitating sphaleron-antisphaleron pair, chain and vortex ring solutions. In these static axially symmetric solutions, the Higgs field vanishes on isolated points on the symmetry axis, or on rings centered around the symmetry axis. We compare these solutions to gravitating monopole-antimonopole systems, associating monopole-antimonopole pairs with sphalerons.Comment: 7 pages, 3 figure