Coupling-induced bipartite pointer states in arrays of electron billiards: quantum Darwinism in action?

We discuss a quantum system coupled to the environment, composed of an open array of billiards (dots) in series. Beside pointer states occurring in individual dots, we observe sets of robust states which arise only in the array. We define these new states as bipartite pointer states, since they cannot be described in terms of simple linear combinations of robust single-dot states. The classical existence of bipartite pointer states is confirmed by comparing the quantum-mechanical and classical results. The ability of the robust states to create "offspring" indicates that quantum Darwinism is in action.     

Dynamical scaling of the quantum Hall plateau transition

Using different experimental techniques, we examine the dynamical scaling of the quantum Hall plateau transition in a frequency range f=0.1-55 GHz. We present a scheme that allows for a simultaneous scaling analysis of these experiments and all other data in literature. We observe a universal scaling function with an exponent kappa=0.5+/-0.1, yielding a dynamical exponent z=0.9+/-0.2.     

Draining of the sea of chaos: role of resonant transmission and reflection in an array of billiards

We investigate the dynamics of a system of coupled electron billiards by using a magnetic field to dramatically modify the underlying mixed phase space. At specific values of the magnetic field the sea of chaos is drained. At these fields there exist reflected or transmitted orbits associated with maxima and minima in the experimentally observed magnetoresistance. These effects are studied by comparing the classical and quantum-mechanical phase-space dynamics leading to a basic understanding of the role of chaos in the transport in an array of billiards.     

Black Hole Formation by Canonical Dynamics of Gravitating Shells: An Equatorial View

Gravitating shells lead to simple minisuperspacemodels of black hole formation by gravitational collapseof matter. I interpret here the Hajicek–Kijowskivariational principle for spacetime with a shell as a Dirac–ADM action principle along atimelike foliation including the shell as a leaf. Byreducing this action by spherical symmetry, I obtain theHamiltonian constraint of a collapsing dust shell and use it as a prelude to canonicalquantization.     

Synthesis,Reactivity and Antimicrobial Activity of a Series of 2-Arylamino-1,3-selenazoles

A series of 2-arylamino-1,3-selenazoles was synthesized and their reactivity was studied. The 2-arylamino-1,3-selenazoles and their reaction products were characterized by various spectroscopic methods and X-ray diffraction. In addition, the antimicrobial activity of the 2-arylamino-1,3-selenazoles in a panel of seven bacteria and fungi was examined.     

Tuning the flow of light in semiconductor-based photonic crystals by magnetic fields

Tuning the flow of light by external fields is a challenging task for scientific studies and optical applications, but it is important in many applications such as switches, modulators, and slow wave structures. Here, new results are presented which demonstrate that this effectively can be achieved by external magnetic fields in one-dimensional photonic crystals made from semiconducting material. The advantage of using semiconducting material is the magnetic-field dependent dielectric function of the free charge carriers particularly where the magnetic field causes large and strongly varying contributions – near the plasma frequency and the cyclotron resonance frequency. The results of simulations on the basis of a multiple scattering method at infrared and microwave frequencies and of experiments on Indium Antimonide in the latter frequency regime confirm the tunability up to the extreme case from full transparency to opaqueness and vice versa.     

Rapid solidification of cryolite and cryolite–alumina melts

Abstract  

Rapid solidification processing (with a cooling rate in the interval 10⁵–10⁶ K s⁻¹) was used to prepare deeply undercooled cryolite–alumina melts. These samples were analyzed by XRD, infrared, and Raman spectroscopy. Besides cryolite, the amorphous phase and a low amount of ι-Al₂O₃ were detected. Annealing of the quenched sample revealed the transformation of metastable amorphous phases into different products depending on the annealing conditions. The results obtained showed that all of the elements (Na, Al, O, and F) are probably present in the amorphous parts of the quenched samples.     

The microwave Hall effect of a two-dimensional electron gas

The integer Quantum Hall effect has been recently observed in the Hall conductivity _xy at microwave frequencies. Here we present a calculation of the wave propagation in the crossed waveguide system used in the experiments. The field pattern is more complicated than in the case of a pure plane wave. The essential result, however, remains unchanged: The field strength in the second (crossed) waveguide is proportional to _xy of the two-dimensional electron gas. Dedicated to Professor Karlheinz Seeger on the occasion of his 60th birthday