The states 1^1\Sigma^+_u, 1^1\Pi_u and 2^1\Sigma^+_u of Sr_2 studied by Fourier-transform spectroscopy

A high resolution study of the electronic states 1^1\Sigma^+_u and 1^1\Pi_u which belong to the asymptote 4^1D + 5^1S and of the state 2(A)^1\Sigma^+_u, which correlates to the asymptote 5^1P + 5^1S, is performed by Fourier-transform spectroscopy of fluorescence progressions induced by single frequency laser excitation. Precise descriptions of the potentials up to 2000 cm^{-1} above the bottom are derived and compared to currently available ab initio calculations. Especially for the state 1^1\Sigma^+_u large deviations are found. Rather weak and local perturbations are observed for the states 1^1\Pi_u and 2^1\Sigma^+_u, while a strong coupling of the state 1^1\Sigma^+_u to the component \Omega=0^+_u of the state 1^3\Pi_u, which belongs to the asymptote 5^3P + 5^1S, is indicated.Comment: Typing errors corrected (including numbers in table IX), 12 pages, 9 figure

Proactive Quality Guidance for Model Evolution in Model Libraries

Model evolution in model libraries differs from general model evolution. It limits the scope to the manageable and allows to develop clear concepts, approaches, solutions, and methodologies. Looking at model quality in evolving model libraries, we focus on quality concerns related to reusability. In this paper, we put forward our proactive quality guidance approach for model evolution in model libraries. It uses an editing-time assessment linked to a lightweight quality model, corresponding metrics, and simplified reviews. All of which help to guide model evolution by means of quality gates fostering model reusability.Comment: 10 pages, figures. Appears in Models and Evolution Workshop Proceedings of the ACM/IEEE 16th International Conference on Model Driven Engineering Languages and Systems, Miami, Florida (USA), September 30, 201

Detectability of strange matter in heavy ion experiments

We discuss the properties of two distinct forms of hypothetical strange matter, small lumps of strange quark matter (strangelets) and of hyperon matter (metastable exotic multihypernuclear objects: MEMOs), with special empha- sis on their relevance for present and future heavy ion experiments. The masses of small strangelets up to AB = 40 are calculated using the MIT bag model with shell mode filling for various bag parameters. The strangelets are checked for possible strong and weak hadronic decays, also taking into account multiple hadron decays. It is found that strangelets which are stable against strong decay are most likely highly negative charged, contrary to previous findings. Strangelets can be stable against weak hadronic decay but their masses and charges are still rather high. This has serious impact on the present high sensitivity searches in heavy ion experiments at the AGS and CERN facilities. On the other hand, highly charged MEMOs are predicted on the basis of an extended relativistic mean field model. Those objects could be detected in future experiments searching for short lived, rare composites. It is demonstrated that future experiments can be sensitive to a much wider variety of strangelets

The interaction of multiple stellar winds in stellar clusters: potential flow

While several studies have investigated large-scale cluster winds resulting from an intra-cluster interaction of multiple stellar winds, as yet they have not provided details of the bordering flows inside a given cluster. The present work explores the principal structure of the combined flow resulting from the interaction of multiple stellar winds inside stellar clusters. The theory of complex potentials is applied to analytically investigate stagnation points, boundaries between individual outflows, and the hydrodynamic structure of the asymptotic large-scale cluster wind. In a second part, these planar considerations are extended to fully three-dimensional, asymmetric configurations of wind-driving stars. We find (i) that one can distinguish regions in the large-scale cluster wind that are determined by the individual stellar winds, (ii) that there are comparatively narrow outflow channels, and (iii) that the large-scale cluster wind asymptotically approaches spherical symmetry at large distances. The combined flow inside a stellar cluster resulting from the interaction of multiple stellar winds is highly structured.Comment: 8 pages, 8 Figure