Topological characterizations of ωμ-metrizable spaces

AbstractThis paper is a detailed elaboration of a talk given by the second author at the Oxford conference in June 1989. It presents necessary and sufficient conditions for a topological space to be ωμ-metrizable (μ> 0), i.e., linearly uniformizable with uncountable uniform weight. In other words, such spaces are exactly those which can be metrized by a distance function taking its values in a totally ordered Abelian group with cofinality ωμ. (For ωμ = ω0, we obtain characterizations of strongly zero-dimensional metric spaces, i.e., nonarchimedeanly metrizable spaces.)It turns out that (strong) suorderability and the existence of a σ-discrete (respectively ωμ- discrete) dense subspace are the most interesting properties in this respect, whenever ωμ > ω0, or ωμ = ω0 and dim X = 0. Therefore, a main part of the paper is devoted to the study of GO-spaces having a σ-discrete (ωμ) dense subspace (Section 3). The last section (Section 4) is concerned with the characterization of ωμ-metrizability in the realm of generalized metric spaces, in particular, by using g-functions.Since all our spaces are zero-dimensional, the paper also contributes results to this important class of spaces, in particular, to the class of nonarchimedean topological spaces

Transverse beam tails due to inelastic scattering

Non-Gaussian beam tails producing low beam lifetimes and background to the experimental detectors can be a serious performance limitation in colliding beam facilities. We describe simulations and measurement of non-Gaussian beam tails, performed on the e+ e- collider LEP, that revealed the importance of inelastic particule scattering as launching processes of particules to large amplitude

Bose-Einstein condensate coupled to a nanomechanical resonator on an atom chip

We theoretically study the coupling of Bose-Einstein condensed atoms to the mechanical oscillations of a nanoscale cantilever with a magnetic tip. This is an experimentally viable hybrid quantum system which allows one to explore the interface of quantum optics and condensed matter physics. We propose an experiment where easily detectable atomic spin-flips are induced by the cantilever motion. This can be used to probe thermal oscillations of the cantilever with the atoms. At low cantilever temperatures, as realized in recent experiments, the backaction of the atoms onto the cantilever is significant and the system represents a mechanical analog of cavity quantum electrodynamics. With high but realistic cantilever quality factors, the strong coupling regime can be reached, either with single atoms or collectively with Bose-Einstein condensates. We discuss an implementation on an atom chip.Comment: published version (5 pages, 3 figures

Observations and simulations of beam tails in LEP

Transverse beam tails have been measured in LEP using scraping collimators and loss monitors. Very significant non-Gaussian tails are present for colliding beams and high beam-beam tune shift. On a lower but still significant level, non-Gaussian tails are also present in the horizontal plane for a single beam. Comparison of measurements with detailed simulations allowed us to identify off-momentum particles produced by scattering processes as a source of significant transverse tails

Program user's manual for optimizing the design of a liquid or gaseous propellant rocket engine with the automated combustor design code AUTOCOM

This computer program manual describes in two parts the automated combustor design optimization code AUTOCOM. The program code is written in the FORTRAN 4 language. The input data setup and the program outputs are described, and a sample engine case is discussed. The program structure and programming techniques are also described, along with AUTOCOM program analysis

Dynamical Instability in a Trimeric Chain of Interacting Bose-Einstein Condensates

We analyze thoroughly the mean-field dynamics of a linear chain of three coupled Bose-Einstein condensates, where both the tunneling and the central-well relative depth are adjustable parameters. Owing to its nonintegrability, entailing a complex dynamics with chaos occurrence, this system is a paradigm for longer arrays whose simplicity still allows a thorough analytical study.We identify the set of dynamics fixed points, along with the associated proper modes, and establish their stability character depending on the significant parameters. As an example of the remarkable operational value of our analysis, we point out some macroscopic effects that seem viable to experiments.Comment: 5 pages, 3 figure

Trapping cold atoms near carbon nanotubes: thermal spin flips and Casimir-Polder potential

We investigate the possibility to trap ultracold atoms near the outside of a metallic carbon nanotube (CN) which we imagine to use as a miniaturized current-carrying wire. We calculate atomic spin flip lifetimes and compare the strength of the Casimir-Polder potential with the magnetic trapping potential. Our analysis indicates that the Casimir-Polder force is the dominant loss mechanism and we compute the minimum distance to the carbon nanotube at which an atom can be trapped.Comment: 8 pages, 3 figure