Classical diamagnetism, magnetic interaction energies, and repulsive forces in magnetized plasmas

The Bohr-van Leeuwen theorem is often summarized as saying that there is no classical magnetic susceptibility, in particular no diamagnetism. This is seriously misleading. The theorem assumes position dependent interactions but this is not required by classical physics. Since the work of Darwin in 1920 it has been known that the magnetism due to classical charged point particles can only be described by allowing velocity dependent interactions in the Lagrangian. Legendre transformation to an approximate Hamiltonian can give an estimate of the Darwin diamagnetism for a system of charged point particles. Comparison with experiment, however, requires knowledge of the number of classically behaving electrons in the sample. A new repulsive effective many-body force, which should be relevant in plasmas, is predicted by the Hamiltonian.Comment: added references, revise

Orthogonality relations for triple modes at dielectric boundary surfaces

We work out the orthogonality relations for the set of Carniglia-Mandel triple modes which provide a set of normal modes for the source-free electromagnetic field in a background consisting of a passive dielectric half-space and the vacuum, respectively. Due to the inherent computational complexity of the problem, an efficient strategy to accomplish this task is desirable, which is presented in the paper. Furthermore, we provide all main steps for the various proofs pertaining to different combinations of triple modes in the orthogonality integral.Comment: 15 page

On Loop Quantum Gravity Phenomenology and the Issue of Lorentz Invariance

A simple model is constructed which allows to compute modified dispersion relations with effects from loop quantum gravity. Different quantization choices can be realized and their effects on the order of corrections studied explicitly. A comparison with more involved semiclassical techniques shows that there is agreement even at a quantitative level. Furthermore, by contrasting Hamiltonian and Lagrangian descriptions we show that possible Lorentz symmetry violations may be blurred as an artifact of the approximation scheme. Whether this is the case in a purely Hamiltonian analysis can be resolved by an improvement in the effective semiclassical analysis.Comment: 16 pages, RevTeX

Strain tuning of topological band order in cubic semiconductors

We theoretically explore the possibility of tuning the topological order of cubic diamond/zinc-blende semiconductors with external strain. Based on the tight-binding model, we analyze the evolution of the cubic semiconductor band structure under hydrostatic or biaxial lattice expansion, by which a generic guiding principle is established that lattice \emph{expansion} can induce a topological phase transition of small band-gap cubic semiconductors via a band inversion, and further breaking of the cubic symmetry leads to a topological insulating phase. Using density functional theory calculations, we demonstrate that a prototype topological trivial semiconductor, InSb, is converted to a nontrivial topological semiconductor with a 2%-3% biaxial lattice expansion.Comment: 4 pages, 3 figure

Nephritogenic autoantibodies but absence of nephritis in Il-12p35–deficient mice with pristane-induced lupus

Nephritogenic autoantibodies but absence of nephritis in Il-12p35–deficient mice with pristane-induced lupus.BackgroundThere is strong evidence that Th1 cytokines are essential for disease in murine models of lupus. Interleukin-12 (IL-12) is essential for Th1 cell differentiation and induces interferon-γ (IFN-γ) production. Paradoxically, it has been suggested that an IL-12 defect drives the pathogenesis of lupus, although its precise role remains unclear. We investigated the role of IL-12 for lupus-like disease induced by pristane. IL-12p35–deficient (-/-) and control (+/+) BALB/c mice were treated with pristane or phosphate-buffered saline (PBS).MethodsProteinuria was measured and renal pathology evaluated 10 months after treatment. Sera were analyzed for autoantibodies and total immunoglobulin levels. Cytokine expression and production was analyzed.ResultsPristane induced nephritogenic autoantibodies and renal immunoglobulin and complement deposition in both IL-12 -/- and +/+ mice. However, proliferative pathology and proteinuria were absent in IL-12-/- mice, whereas pristane induced severe nephritis in one third of the +/+ mice. As expected, cytokine balance was skewed toward a Th2 response in pristane-treated IL-12 -/- mice.ConclusionThese data indicate that renal immune complex deposition can occur in the absence of IL-12p35, but that structural renal damage requires the presence of IL-12p35 or mediators induced by this molecule, such as IFN-γ. In contrast to the abrogation of nephritogenic autoantibodies by the lack of IFN-γ, such antibodies are induced by pristane in IL-12p35–deficient mice. Absence of structural renal disease, despite the presence of nephritogenic autoantibodies in pristane-treated IL-12-/- mice, indicates that antibody deposition alone is not sufficient for the development of lupus nephritis in this model

Weak antilocalization and disorder-enhanced electron interactions in crystalline GeSbTe

Phase change materials can be reversibly switched between amorphous and crystalline states and often show strong contrast in the optical and electrical properties of these two phases. They are now in widespread use for optical data storage, and their fast switching and a pronounced change of resistivity upon crystallization are also very attractive for nonvolatile electronic data storage. Nevertheless there are still several open questions regarding the electronic states and charge transport in these compounds. In this work we study electrical transport in thin metallic films of the disordered, crystalline phase change material Ge$_1$Sb$_2$Te$_4$. We observe weak antilocalization and disorder enhanced Coulomb interaction effects at low temperatures, and separate the contributions of these two phenomena to the temperature dependence of the resistivity, Hall effect, and magnetoresistance. Strong spin-orbit scattering causes positive magnetoresistance at all temperatures, and a careful analysis of the low-field magnetoresistance allows us to extract the temperature dependent electron dephasing rate and study other scattering phenomena. We find electron dephasing due to inelastic electron-phonon scattering at higher temperatures, electron-electron scattering dephasing at intermediate temperatures, and a crossover to weak temperature dependence below 1 K

On the Wake Structure in Streaming Complex Plasmas

The theoretical description of complex (dusty) plasmas requires multiscale concepts that adequately incorporate the correlated interplay of streaming electrons and ions, neutrals, and dust grains. Knowing the effective dust-dust interaction, the multiscale problem can be effectively reduced to a one-component plasma model of the dust subsystem. The goal of the present publication is a systematic evaluation of the electrostatic potential distribution around a dust grain in the presence of a streaming plasma environment by means of two complementary approaches: (i) a high precision computation of the dynamically screened Coulomb potential from the dynamic dielectric function, and (ii) full 3D particle-in-cell simulations, which self-consistently include dynamical grain charging and non-linear effects. The applicability of these two approaches is addressed

Non-Markoffian effects of a simple nonlinear bath

We analyze a model of a nonlinear bath consisting of a single two-level system coupled to a linear bath (a classical noise force in the limit considered here). This allows us to study the effects of a nonlinear, non-Markoffian bath in a particularly simple situation. We analyze the effects of this bath onto the dynamics of a spin by calculating the decay of the equilibrium correlator of the spin's z-component. The exact results are compared with those obtained using three commonly used approximations: a Markoffian master equation for the spin dynamics, a weak-coupling approximation, and the substitution of a linear bath for the original nonlinear bath.Comment: 7 pages, 6 figure

Identifying Drivers of Seasonality in Lena River Biogeochemistry and Dissolved Organic Matter Fluxes

Warming air temperatures, shifting hydrological regimes and accelerating permafrost thaw in the catchments of the Arctic rivers is affecting their biogeochemistry. Arctic river monitoring is necessary to observe changes in the mobilization of dissolved organic matter (DOM) from permafrost. The Lena River is the second largest Arctic river and 71% of its catchment is continuous permafrost. Biogeochemical parameters, including temperature, electrical conductivity (EC), stable water isotopes, dissolved organic carbon (DOC) and absorption by colored dissolved organic matter (aCDOM) have been measured as part of a new high-frequency sampling program in the central Lena River Delta. The results show strong seasonal variations of all biogeochemical parameters that generally follow seasonal patterns of the hydrograph. Optical indices of DOM indicate a trend of decreasing aromaticity and molecular weight from spring to winter. High-frequency sampling improved our estimated annual fluvial flux of annual dissolved organic carbon flux (6.79 Tg C). EC and stable isotope data were used to distinguish three different source water types which explain most of the seasonal variation in the biogeochemistry of the Lena River. These water types match signatures of (1) melt water, (2) rain water, and (3) subsurface water. Melt water and rain water accounted for 84% of the discharge flux and 86% of the DOC flux. The optical properties of melt water DOM were characteristic of fresh organic matter. In contrast, the optical properties of DOM in subsurface water revealed lower aromaticity and lower molecular weights, which indicate a shift toward an older organic matter source mobilized from deeper soil horizons or permafrost deposits. The first year of this new sampling program sets a new baseline for flux calculations of dissolved matter and has enabled the identification and characterization of water types that drive the seasonality of the Lena River water properties

Mechanics, cosmology and Mach's principle

It is pointed out that recent cosmological findings seem to support the view that the mass/energy distribution of the universe defines the Newtonian inertial frames as originally suggested by Mach. The background concepts of inertial frame, Newton's second law, and fictitious forces are clarified. A precise definition of Mach's principle is suggested. Then an approximation to general relativity discovered by Einstein, Infeld, and Hoffmann is used and it is found that this precise formulation of Mach's principle is realized provided the mass/energy density of the universe has a specific value. This value turns out to be twice the critical density. The implications of this approximate result is put into context.Comment: 9 pages, 34 references, 0 figure