Vortex glass transition in a random pinning model

We study the vortex glass transition in disordered high temperature superconductors using Monte Carlo simulations. We use a random pinning model with strong point-correlated quenched disorder, a net applied magnetic field, long-range vortex interactions, and periodic boundary conditions. From a finite size scaling study of the helicity modulus, the rms current, and the resistivity, we obtain critical exponents at the phase transition. The new exponents differ substantially from those of the gauge glass model, but are close to those of the pure three-dimensional XY model.     

Properties of Removable Singularities for Hardy Spaces of Analytic Functions

Removable singularities for Hardy spaces H^p() = {f Hol(): |f|^p u in for some harmonic u}, 0 < p < are studied. A setE = is a weakly removable singularity for H^p(\E) if H^p(\E) Hol(), and a strongly removable singularity for H^p(\E) if H^p(\E)= H^p(). The two types of singularities coincide for compactE, and weak removability is independent of the domain . The paper looks at differences between weak and strong removability,the domain dependence of strong removability, and when removabilityis preserved under unions. In particular, a domain and a setE that is weakly removable for all H^p, but not strongly removablefor any H^p(\E), 0 < p < , are found. It is easy to show that if E is weakly removable for H^p(\E)and q > p, then E is also weakly removable for H^q(\E). Itis shown that the corresponding implication for strong removabilityholds if and only if q/p is an integer. Finally, the theory of Hardy space capacities is extended, anda comparison is made with the similar situation for weightedBergman spaces.     

High-speed heck reactions in ionic liquid with controlled microwave heating

Palladium-catalyzed Heck arylations in the polar and robust ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF(6)), have for the first time been accomplished under microwave irradiation. The couplings were efficiently performed in sealed tubes within 5-45 min of heating. Without significant reductions in yield, a phosphine-free ionic catalyst phase could be recycled in five successive 20 min reactions at 180 degrees C. The product was easily removed from the reaction medium by distillation.     

Absolutely continuous measures on non quasi-analytic curves with independent powers

We prove that every non quasi-analytic Carleman class contains functions whose graph supports measures that are absolutely continuous with respect to arc length measure and yet they have independent convolution powers in the measure algebra . The proof relies on conditions which ensure that the canonical map between two Cantor sets can be extended to a function in an arbitrary prescribed non quasi-analytic Carleman class.

     

Call for papers Special issue on “Quantum interference and cryptographic keys: novel physics and advancing technologies"

The collective phenomena of quantum interference, including wave particle duality and apparent non-locality, have intrigued the physics community for many years. It is only recently that we have begun to turn these somewhat counter intuitive quantum phenomena to good use. A leading force in that direction is quantum cryptography - absolute secure key exchange encoding data on the polarisation or phase of individual photons, or using the quantum correlations between pairs of particles. Technologies are now implemented to bring the various forms of quantum cryptography to commercial application. At the same time the possibility of communications applications has stimulated the study of a variety of novel quantum interference phenomena. Quantum information experiments involving two, three and four photons are planned and a novel Field of continuous variable (many photon) quantum information has emerged. These various aspects of quantum cryptography are considered in the conference “QUICK: Quan- tum interference and cryptographic keys: novel physics and advancing technologies", taking place in Cargese from April 7 to 13, 2001. Following that conference, we invite submission of original papers to a special issue of the European Physical Journal D, on the following topics: - quantum cryptography technologies, - quantum cryptography systems, - free space quantum cryptography and satellites, - pair-photon sources and multiphoton interference, - single photon sources, - continuous variable quantum information, - security aspects, - cryptographic protocols, - entanglement purification in cryptographic schemes, - novel physics and quantum gates for photonic qubits. The submitted articles should be sent to the EPJ D Editorial Office in Orsay. The deadline is July 15, 2001. We look forward to a stimulating special issue.     

The structure of calcium-ammonia solutions by neutron diffraction

The microscopic structures of calcium-ammonia solutions have been established by using neutron diffraction. Total structure factors measured at 230 K reveal immediately the evolution of an uncommonly intense diffraction prepeak in the metallic solutions. As concentration is increased from 4 mole percent metal to 10 mole percent metal (i.e., saturation), this feature intensifies and shifts from 0.6 to 0.9 A(-1). It is therefore evidence of well developed intermediate-range ordering among the solvated cations, and is a microstructural signature of the observed strong phase separation of metallic (concentrated) and nonmetallic (dilute) solutions. The technique of isotopic labelling of *N by 15N was then used in conjunction with difference analysis to focus on the solvent structure in metallic solutions at 4 and 10 mole percent metal. These nitrogen-centered functions are analyzed in conjunction with classical Monte Carlo computer simulation techniques, to provide us with detailed insight into the calcium solvation and the extent of hydrogen bonding. We find that calcium is solvated by approximately 6-7 ammonia molecules, with a Ca-N distance of around 2.45 A. There is evidence of hydrogen bonding among the solvent molecules, even in the saturated 10 mole percent metal solution.