Phase transitions in experimental systems

Scaling functions of the support and of the measure have been used to characterize the scaling behavior of a dynamical system. While scaling functions for the scaling of the measure, ƒ(), have been calculated for a number of experimental systems, examples of scaling functions φ(λ) for the scaling of the support are difficult to obtain. In this contribution, we report on a phase-transition-like effect of an experimental p-doped germanium semiconductor sample. It is found that the results obtained from the dynamical scaling function agree with those obtained by Horita et al. from model maps, indicating that scaling functions for the scaling of the support are a powerful method of characterizing experimental dynamical systems.     

The radiation of rotating magnetic dipoles in vacuo in general relativity

An approximate solution of Maxwell's equations for the rotating oblique magnetic dipole is given on the geometrical background of the Schwarzschild metric. The energy radiation is calculated for both the case of the Schwarzschild geometry and the linearized Kerr metric on the basis of the Newman-Penrose formalism. It is shown that general relativistic effects are not sufficient to explain by themselves the experimentally measured slowdown laws of realistic pulsars.     

The impact parameter dependence of the Pb + Pb K − MO spectrum

Molecular orbital X-rays are emitted during ion-atom collisions. The theoretical treatment, numerical results for the Pb + Pb system and a comparison with background radiation like NNB, SEB and γ-decay of Coulomb excited nuclei are presented.     

Calculation of wavefunctions and frequencies for noninfinitesimal vibrations: Comparison of various methods using ab initio CI potential curves

Three computational methods employing different means of representing molecular potentials are used to obtain wavefunctions and energy levels for noninfinitesimal vibrations. An interpolation scheme based on a cubic spline fitting procedure is introduced to supplement the CI energy results obtained explicitly in actual calculations. As long as a representative set of potential points is available it is found that the results of all three methods (two of variational and one of numerical integration type) are quite consistent, for both bending and stretching vibrations of ground and electronically excited states (examples for HCN and O₂ are considered). In addition a comparison of one- and two-dimensional bending vibrational treatments is made.     

Conductivity in an activity gradient

A procedure to evaluate conductivity measurements on a sample exposed to an activity gradient is presented The method allows the measured mean conductivity to be subsequently associated with a denned activity It offers not only an experimentally simple alternative to the Wagner-Hebb experiment, but also enables detailed information to be obtained about the activity dependence of the conductivity in polarization measurements with two blocking electrodes as well as in concentration cell experiments, no matter whether a two- or four-point arrangement is used It is further shown how the steady-state activities, which are necessary to compute the desired mean value, can be obtained from the initial and boundary conditions     

A nonvanishing theorem for the cuspidal cohomology of SL2 over imaginary quadratic integers

Mathematische Annalen -     

Friction and diffusion of matter-wave bright solitons

We consider the motion of a matter-wave bright soliton under the influence of a cloud of thermal particles. In the ideal one-dimensional system, the scattering process of the quasiparticles with the soliton is reflectionless; however, the quasiparticles acquire a phase shift. In the realistic system of a Bose-Einstein condensate confined in a tight waveguide trap, the transverse degrees of freedom generate an extra nonlinearity in the system which gives rise to finite reflection and leads to dissipative motion of the soliton. We calculate the velocity and temperature-dependent frictional force and diffusion coefficient of a matter-wave bright soliton immersed in a thermal cloud.     

Three-dimensional polarization-independent visible-frequency carpet invisibility cloak

We miniaturize all features in a previously introduced polarization-independent three-dimensional carpet invisibility cloak by more than a factor of 2. This leads to operation wavelengths in the visible. The structures are characterized by electron and optical microscopy. In contrast to our previous work at IR wavelengths, we can directly measure two-dimensional images at visible frequencies, perform control experiments from the backside, and compare the images with theory. We find excellent agreement. Furthermore, we study the wavelength dependence in the range from 900 nm down to 500 nm. Cloaking action deteriorates as the woodpile stop band at around 575 nm is approached.     

In situ characterization of semiconductor saturable absorber mirrors in an operating Yb:KGW mode-locked laser

We report in situ characterization of a semiconductor saturable absorber mirror (SESAM) in an operating Yb:KGW mode-locked laser. The technique may be described as a pump-probe experiment in which the intracavity beam acts as a pump beam while the output of the same laser is used as a test beam for the SESAM reflectivity. At zero delay, the probe pulse overlaps in time with the subsequent intracavity pulse. The method is an alternative to standard pump-probe measurements in situations where the intracavity parameters such as energy fluence onto the SESAM, pulse length, and center wavelength cannot be achieved simultaneously with available lasers.