Perturbative Expansion in the Galilean Invariant Spin One-Half Chern-Simons Field Theory

A Galilean Chern-Simons field theory is formulated for the case of two interacting spin-1/2 fields of distinct masses M and M'. A method for the construction of states containing N particles of mass M and N' particles of mass M' is given which is subsequently used to display equivalence to the spin-1/2 Aharonov-Bohm effect in the N = N' =1 sector of the model. The latter is then studied in perturbation theory to determine whether there are divergences in the fourth order (one loop) diagram. It is found that the contribution of that order is finite (and vanishing) for the case of parallel spin projections while the antiparallel case displays divergences which are known to characterize the spin zero case in field theory as well as in quantum mechanics.Comment: 14 pages LaTeX, including 2 figures using eps

What treatments are effective for varicose veins?

For larger trunk varicose veins, as in the saphenous vein, therapeutic options include conservative measures (such as leg elevation and compression stockings), injection sclerotherapy, and surgical vein ligation, with or without stripping.Long-term outcomes appear superior with surgical treatment. For mid-sized reticular veins and spider telangiectasias, several options are available, including sclerotherapy, laser ablation, and thermal ablation. However, no randomized trials have compared the relative effectiveness of these treatments. Venotonic medications (primarily plantderived and synthetic flavonoids, such as horse chestnut seed extract, that improve venous tone) provide symptom relief. Head- to-head comparisons are needed to identify the most efficacious therapies (strength of recommendation: C, based on case series and extrapolations from small trials.

Month-Timescale Optical Variability in the M87 Jet

A previously inconspicuous knot in the M87 jet has undergone a dramatic outburst and now exceeds the nucleus in optical and X-ray luminosity. Monitoring of M87 with the Hubble Space Telescope and Chandra X-ray Observatory during 2002-2003, has found month-timescale optical variability in both the nucleus and HST-1, a knot in the jet 0.82'' from the nucleus. We discuss the behavior of the variability timescales as well as spectral energy distribution of both components. In the nucleus, we see nearly energy-independent variability behavior. Knot HST-1, however, displays weak energy dependence in both X-ray and optical bands, but with nearly comparable rise/decay timescales at 220 nm and 0.5 keV. The flaring region of HST-1 appears stationary over eight months of monitoring. We consider various emission models to explain the variability of both components. The flares we see are similar to those seen in blazars, albeit on longer timescales, and so could, if viewed at smaller angles, explain the extreme variability properties of those objects.Comment: 4 pages, 3 figures, ApJ Lett., in pres

Atomic layer deposition of metals: Precursors and film growth

The coating of complex three-dimensional structures with ultrathin metal films is of great interest for current technical applications, particularly in microelectronics, as well as for basic research on, for example, photonics or spintronics. While atomic layer deposition (ALD) has become a well-established fabrication method for thin oxide films on such geometries, attempts to develop ALD processes for elemental metal films have met with only mixed success. This can be understood by the lack of suitable precursors for many metals, the difficulty in reducing the metal cations to the metallic state, and the nature of metals as such, in particular their tendency to agglomerate to isolated islands. In this review, we will discuss these three challenges in detail for the example of Cu, for which ALD has been studied extensively due to its importance for microelectronic fabrication processes. Moreover, we give a comprehensive overview over metal ALD, ranging from a short summary of the early research on the ALD of the platinoid metals, which has meanwhile become an established technology, to very recent developments that target the ALD of electropositive metals. Finally, we discuss the most important applications of metal ALD

Covariance systems

We introduce new definitions of states and of representations of covariance systems. The GNS-construction is generalized to this context. It associates a representation with each state of the covariance system. Next, states are extended to states of an appropriate covariance algebra. Two applications are given. We describe a nonrelativistic quantum particle, and we give a simple description of the quantum spacetime model introduced by Doplicher et al.Comment: latex with ams-latex, 23 page

Chiral three-nucleon forces and bound excited states in neutron-rich oxygen isotopes

We study the spectra of neutron-rich oxygen isotopes based on chiral two- and three-nucleon interactions. First, we benchmark our many-body approach by comparing ground-state energies to coupled-cluster results for the same two-nucleon interaction, with overall good agreement. We then calculate bound excited states in 21,22,23O, focusing on the role of three-nucleon forces, in the standard sd shell and an extended sdf7/2p3/2 valence space. Chiral three-nucleon forces provide important one- and two-body contributions between valence neutrons. We find that both these contributions and an extended valence space are necessary to reproduce key signatures of novel shell evolution, such as the N = 14 magic number and the low-lying states in 21O and 23O, which are too compressed with two-nucleon interactions only. For the extended space calculations, this presents first work based on nuclear forces without adjustments. Future work is needed and open questions are discussed.Comment: 6 pages, 4 figures, published versio