Island formation without attractive interactions

We show that adsorbates on surfaces can form islands even if there are no attractive interactions. Instead strong repulsion between adsorbates at short distances can lead to islands, because such islands increase the entropy of the adsorbates that are not part of the islands. We suggest that this mechanism cause the observed island formation in O/Pt(111), but it may be important for many other systems as well.Comment: 11 pages, 4 figure

Graph-Based Shape Analysis Beyond Context-Freeness

We develop a shape analysis for reasoning about relational properties of data structures. Both the concrete and the abstract domain are represented by hypergraphs. The analysis is parameterized by user-supplied indexed graph grammars to guide concretization and abstraction. This novel extension of context-free graph grammars is powerful enough to model complex data structures such as balanced binary trees with parent pointers, while preserving most desirable properties of context-free graph grammars. One strength of our analysis is that no artifacts apart from grammars are required from the user; it thus offers a high degree of automation. We implemented our analysis and successfully applied it to various programs manipulating AVL trees, (doubly-linked) lists, and combinations of both

The eta' meson from lattice QCD

We study the flavour singlet pseudoscalar mesons from first principles using lattice QCD. With N_f=2 flavours of light quark, this is the so-called eta_2 meson and we discuss the phenomenological status of this. Using maximally twisted-mass lattice QCD, we extract the mass of the eta_2 meson at two values of the lattice spacing for lighter quarks than previously discussed in the literature. We are able to estimate the mass value in the limit of light quarks with their physical masses.Comment: 16 pages: version accepted for publicatio

Lifeview and perception of message in drama

The age-old controversy between church and the arts has not been resolved by a long shot. The ethically repellent in modern art is definitely over-emphasized at the cost of the ethically acceptable. This leads to the question about the Chri­stian response to a play with a non-Christian lifeview, one in which the charac­ters use crude language and in which vulgar actions are indulged in

Upper critical field in {Ba1−x_{1-x}Kx_xBiO3_3}: magnetotransport versus magnetotunneling

Elastic tunneling is used as a powerful direct tool to determine the upper critical field $H_{c2}(T)$ in the high-$T_c$ oxide Ba$_{1-x}$K$_x$BiO$_3$. The temperature dependence of $H_{c2}$ inferred from the tunneling follows the Werthamer-Helfand-Hohenberg prediction for type-II superconductors. A comparison will be made with resistively determined critical field data.Comment: 4 pages incl. 5 figure

Phonon-modulated magnetic interactions and spin Tomonaga-Luttinger liquid in the p-orbital antiferromagnet CsO2

The magnetic response of antiferromagnetic CsO2, coming from the p-orbital S=1/2 spins of anionic O2- molecules, is followed by 133Cs nuclear magnetic resonance across the structural phase transition occuring at Ts1=61 K on cooling. Above Ts1, where spins form a square magnetic lattice, we observe a huge, nonmonotonic temperature dependence of the exchange coupling originating from thermal librations of O2- molecules. Below Ts1, where antiferromagnetic spin chains are formed as a result of p-orbital ordering, we observe a spin Tomonaga-Luttinger-liquid behavior of spin dynamics. These two interesting phenomena, which provide rare simple manifestations of the coupling between spin, lattice and orbital degrees of freedom, establish CsO2 as a model system for molecular solids.Comment: 9 pages, 5 figures (with Supplemental Material), to appear in Physical Review Letter

Nieuw peilbeheer in de veenweiden?

Bij het huidige waterbeheer in de veenweidegebieden zal het maaiveld in de komende honderd jaar op veel plaatsen met meer dan een meter dalen. De maaivelddaling gaat door tot al het veen is verdwenen en de minerale ondergrond aan de oppervlakte ligt. Met het veen verdwijnt dan ook het bijbehorende veenlandschap. De enige mogelijkheid om deze ontwikkeling af te remmen, is door het waterpeil te verhogen. Er zijn verschillende waterpeilstrategieën denkbaar om dat te realiseren, maar die hebben de nodige gevolgen voor inrichting, bodemgebruik en waterinlaat. Een strategiestudie brengt momenteel de gevolgen in kaart en biedt daarmee de waterbeheerder handvatten om mogelijke veranderingen in het peilbeheer te beoordele

Nucleon form factors and moments of parton distributions in twisted mass lattice QCD

We present results on the electroweak form factors and on the lower moments of parton distributions of the nucleon, within lattice QCD using two dynamical flavors of degenerate twisted mass fermions. Results are obtained on lattices with three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm, allowing the investigation of cut-off effects. The volume dependence is examined by comparing results on two lattices of spatial length L=2.1 fm and L=2.8 fm. The simulations span pion masses in the range of 260-470 MeV. Our results are renormalized non-perturbatively and the values are given in the MS-scheme at a scale mu=2 GeV.Comment: Talk presented in the XXIst International Europhysics Conference on High Energy Physics, 21-27 July 2011, Grenoble, Rhones Alpes Franc