Discrete conservation properties for shallow water flows using mixed mimetic spectral elements

A mixed mimetic spectral element method is applied to solve the rotating shallow water equations. The mixed method uses the recently developed spectral element histopolation functions, which exactly satisfy the fundamental theorem of calculus with respect to the standard Lagrange basis functions in one dimension. These are used to construct tensor product solution spaces which satisfy the generalized Stokes theorem, as well as the annihilation of the gradient operator by the curl and the curl by the divergence. This allows for the exact conservation of first order moments (mass, vorticity), as well as quadratic moments (energy, potential enstrophy), subject to the truncation error of the time stepping scheme. The continuity equation is solved in the strong form, such that mass conservation holds point wise, while the momentum equation is solved in the weak form such that vorticity is globally conserved. While mass, vorticity and energy conservation hold for any quadrature rule, potential enstrophy conservation is dependent on exact spatial integration. The method possesses a weak form statement of geostrophic balance due to the compatible nature of the solution spaces and arbitrarily high order spatial error convergence

Quantum dynamics of an atomic double-well system interacting with a trapped ion

We theoretically analyze the dynamics of an atomic double-well system with a single ion trapped in its center. We find that the atomic tunnelling rate between the wells depends both on the spin of the ion via the short-range spin-dependent atom-ion scattering length and on its motional state with tunnelling rates reaching hundreds of Hz. A protocol is presented that could transport an atom from one well to the other depending on the motional (Fock) state of the ion within a few ms. This phonon-atom coupling is of interest for creating atom-ion entangled states and may form a building block in constructing a hybrid atom-ion quantum simulator. We also analyze the effect of imperfect ground state cooling of the ion and the role of micromotion when the ion is trapped in a Paul trap. Due to the strong non-linearities in the atom-ion interaction, the micromotion can cause couplings to high energy atom-ion scattering states, preventing accurate state preparation and complicating the double-well dynamics. We conclude that the effects of micromotion can be reduced by choosing ion/atom combinations with a large mass ratio and by choosing large inter-well distances. The proposed double-well system may be realised in an experiment by combining either optical traps or magnetic microtraps for atoms with ion trapping technology.Comment: 14 pages, 13 figure

Topological constraints on magnetostatic traps

We theoretically investigate properties of magnetostatic traps for cold atoms that are subject to externally applied uniform fields. We show that Ioffe Pritchard traps and other stationary points of $B$ are confined to a two-dimensional curved manifold defined by $\det(\partial B_i/\partial x_j)=0$. We describe how stationary points can be moved over the manifold by applying external uniform fields. The manifold also plays an important role in the behavior of points of zero field. Field zeroes occur in two distinct types, in separate regions of space divided by the manifold. Pairs of zeroes of opposite type can be created or annihilated on the manifold. Finally, we give examples of the manifold for cases of practical interest.Comment: 7 pages, 5 figure

Temperature dependence of spin-cluster resonance intensity in RbFeCl3·2H2O

The spin-cluster resonance intensity is observed as a function of temperature in the pseudo-one-dimensional canted Ising metamagnet RbFeCl3·2H2O. For T 0.7 TN a pure one-dimensional Ising model gives a good description of the observed intensities. For T TN the intensity decreases rapidly as a function of temperature due to the destruction of the local ordering around a spin-cluster. The measured value of the intrachain interaction Ja/k of -36 K is in good agreement with earlier measurements on spin-cluster excitations

Bibliometric analyses on repository contents as a library service for the evaluation of research

Since the last two decennia, the library of Wageningen University and Research (or Wageningen UR) has been involved in several bibliometric analyses for the evaluation of scientific output of staff, chair groups, research institutes and graduate schools. In these bibliometric analyses several indicator scores, such as the number of publications, number of citations and citation impacts, are calculated. However, since publication and citation habits differ considerably per scientific discipline, indicator scores need to be standardized in order to make comparison of scientific outputs from staff, chair groups, research institutes or graduate schools, that belong to different scientific disciplines, possible. It is for this reason that Wageningen UR Library bases its bibliometric analyses on indicator scores that are standardized against average trend (or baseline) scores per research field. For the collection of scientific output that is subjected to bibliometric analyses the repository Wageningen Yield (WaY) is used. This repository contains metadata and links to scientific output of the staff, research groups, chair groups and institutes of Wageningen UR and is developed and managed by Wageningen UR Library. By the application of a link between the metadata of publications in WaY and citation scores in Thomson Reuters’ Web of Science, custom-made analyses can be performed efficiently. Usings the repository WaY as a source for Wageningen UR’s scientific output enables optimal use of meta data (e.g. affiliations of authors), improvement of completeness and data quality as well as awareness of library services. Moreover, the bibliometric analyses give insights in steps that can be taken to improve publication strategies for Wageningen UR staff, chair groups, research institutes and graduate schools