On kernel engineering via Paley–Wiener

A radial basis function approximation takes the form $$s(x)=\sum_{k=1}^na_k\phi(x-b_k),\quad x\in {\mathbb{R}}^d,$$ where the coefficients a 1,…,a n are real numbers, the centres b 1,…,b n are distinct points in ℝ d , and the function φ:ℝ d →ℝ is radially symmetric. Such functions are highly useful in practice and enjoy many beautiful theoretical properties. In particular, much work has been devoted to the polyharmonic radial basis functions, for which φ is the fundamental solution of some iterate of the Laplacian. In this note, we consider the construction of a rotation-invariant signed (Borel) measure μ for which the convolution ψ=μ φ is a function of compact support, and when φ is polyharmonic. The novelty of this construction is its use of the Paley–Wiener theorem to identify compact support via analysis of the Fourier transform of the new kernel ψ, so providing a new form of kernel engineering

Fine structure of "zero-mode" Landau levels in HgTe/HgCdTe quantum wells

HgTe/HgCdTe quantum wells with the inverted band structure have been probed using far infrared magneto-spectroscopy. Realistic calculations of Landau level diagrams have been performed to identify the observed transitions. Investigations have been greatly focused on the magnetic field dependence of the peculiar pair of "zero-mode" Landau levels which characteristically split from the upper conduction and bottom valence bands, and merge under the applied magnetic field. The observed avoided crossing of these levels is tentatively attributed to the bulk inversion asymmetry of zinc blend compounds.Comment: 5 pages, 4 figure

Casimir force on amplifying bodies

Based on a unified approach to macroscopic QED that allows for the inclusion of amplification in a limited space and frequency range, we study the Casimir force as a Lorentz force on an arbitrary partially amplifying system of linearly locally responding (isotropic) magnetoelectric bodies. We demonstrate that the force on a weakly polarisable/magnetisable amplifying object in the presence of a purely absorbing environment can be expressed as a sum over the Casimir--Polder forces on the excited atoms inside the body. As an example, the resonant force between a plate consisting of a dilute gas of excited atoms and a perfect mirror is calculated

The Executive Revolving Door: New Dataset on the Career Moves of Former Danish Ministers and Permanent Secretaries

Concerns have been raised that transfers of bureaucrats and politicians into the private sector might create unfair advantages for their future employers and even lead to distrust in government. Not surprisingly, the study of the revolving door has therefore gained prominence in the academic literature. Importantly, however, less attention has been paid to the executive branch. We add to the study of the revolving door by presenting the first dataset on the executive revolving door in Denmark. To do so, we trace the frequency, timing and character of the career moves of Danish Ministers and Permanent Secretaries who held office from 2009 to 2019. Our data document that the Danish executive revolving door is widespread: more than a third of Danish Ministers and Permanent Secretaries end up in a private job within the same year or the year after they stop their job. If we extend the period and investigate the entire period after public service, the number is above 60 percent. Moreover, a substantial share of the jobs obtained is in companies and at a senior level. Our note concludes with reflections on how our data can be used to fill existing research gaps and should be complemented in future research.publishedVersio

The North American toxic fungal pathogen G3 Claviceps purpurea (Fries) Tulasne is established in the German Wadden Sea.

Three lineages (G1, G2 and G3) within the toxic invasive ergot fungus Claviceps purpurea (Fries) Tulasne are known; these should be recognized as unique species, or at least as varieties. On 2 November 2011, a very dense, well established population of G3 C. purpurea was found on the common cord-grass Spartina anglica C.E. Hubbard at two localities on the German North Sea coast in the Wadden Sea (Caciliengroden and Hooksiel). It is most likely that G3 C. purpurea has a North American origin and entered German coastal waters by floating sclerotia from Irish, British, or Benelux waters, where it was previously found. However, introduction via ships’ ballast water coming from their native or introduced ranges is also plausible. Furthermore imports of G3 sclerotia via seed mussels collected from wild subtidal banks in Irish, British and Dutch coastal waters and released into the German Wadden Sea can currently not be excluded. Risks from this highly toxic fungus for human, grazing animals and the marine environment have been identified but not yet quantified in terms of impact. A suitable monitoring programme should be implemented to detect any unwanted impacts caused by G3 C. purpurea in German salt marshes at an early phase

Quantum Correlated Interstitials and the Hall Resistivity of the Magnetically Induced Wigner Crystal

We study a trial wavefunction for an interstitial in a Wigner crystal. We find that the electron correlations, ignored in a conventional Hartree-Fock treatment, dramatically lower the interstitial energy, especially at fillings close to an incompressible liquid state. The correlation between the interstitial electron and the lattice electrons at $\nu <1/m$ is introduced by constructing a trial wave- function which bears a Jastrow factor of a Laughlin state at $\nu=1/m$. For fillings close to but just below $\nu=1/m$, we find that a perfect Wigner crystal becomes unstable against formation of such interstitials. It is argued that conduction due to correlated interstitials in the presence of weak disorder leads to the {\it classical} Hall resistivity, as seen experimentally.Comment: 10 pages, RevTe

Molecular beam epitaxy of high structural quality Bi2Se3 on lattice matched InP(111) substrates

Epitaxial layers of the topological insulator Bi2Se3 have been grown by molecular beam epitaxy on laterally lattice-matched InP(111)B substrates. High resolution X-ray diffraction shows a significant improvement of Bi2Se3 crystal quality compared to layers deposited on other substrates. The measured full width at half maximum of the rocking curve is Delta omega=13 arcsec, and the (omega-2theta) scans exhibit clear layer thickness fringes. Atomic force microscope images show triangular twin domains with sizes increasing with layer thickness. The structural quality of the domains is confirmed on the microscopic level by transmission electron microscopy.Comment: 4 pages, 4 figure

Celebrity Coverage

Celebrity coverage is defined as mediated attention provided to well‐known individuals who through their state of fame become newsworthy. Coverage of celebrities ranges from stories about famous people in categories such as Hollywood, sports, politics, and music as well as celebrities who become famous through digital media. Celebrity journalism focuses on the process of becoming famous, known as the celebrification of individuals, and the influence celebrities have on politics, culture, and activism known as celebritization. Through an increasing interest in its content, celebrity coverage has turned into an economic good for media organizations. While celebrities continue to rely on mass media channels, digital media have changed not only celebrity culture, but also celebrity journalism