1-loop matching of a thermal Lorentz force

Studying the diffusion and kinetic equilibration of heavy quarks within a hot QCD medium profits from the knowledge of a coloured Lorentz force that acts on them. Starting from the spatial components of the vector current, and carrying out two matching computations, one for the heavy quark mass scale (M) and another for thermal scales $$ \left(\sqrt{MT},T\right) $$ MT T , we determine 1-loop matching coefficients for the electric and magnetic parts of a Lorentz force. The magnetic part has a non-zero anomalous dimension, which agrees with that extracted from two other considerations, one thermal and the other in vacuum. The matching coefficient could enable a lattice study of a colour-magnetic 2-point correlator.

Exact holographic RG flows in extended SUGRA

We present a family of exact planar hairy neutral black hole solutions in extended supergravity with Fayet-Iliopoulos (FI) terms. We consider a model where the magnetic part of FI sector vanishes and obtain the superpotential at finite temperature in analytic form. Then, we discuss the thermodynamics and some holographic properties of these solutions. We regularize the action by two different methods, one with gravitational and scalar counterterms and the other using the thermal superpotential as a counterterm, and compute the holographic stress tensor. We also construct the c-function of the corresponding RG flow and obtain an exact holographic β-function for this model.

Definition of conditions of selective iron reduction from iron-manganese ore

The article presents thermodynamic modeling results of reduction roasting of ferromanganese ore with a high phosphorus content in the presence of solid carbon. The modeling was carried out using TERRA software package. Influence of the process temperature in the range 950 – 1300 K and carbon content in the amount of 8.50 – 8.85 g per 100 g of ore on reduction of iron, manganese and phosphorus was investigated. With these parameters of the system, iron is reduced by both solid carbon and carbon monoxide CO to the metallic state, and manganese is reduced only to MnO oxide. The degree of phosphorus reduction depends on the amount of reducing agent. With an excess of carbon relative to the reduction of iron, all phosphorus is converted into metal at a temperature of 1150 K. Phosphorus is not reduced at temperatures below 1150 K and such amount of carbon. The process of solid-phase reduction of iron from manganese ore with the preservation of manganese in the oxide phase was researched in laboratory conditions. Experimental results of direct reduction of these elements with carbon and indirect reduction with carbon monoxide CO are presented. The experiments were carried out in the laboratory Tamman furnace at a temperature of 1000 – 1300 °C and holding time of 1 and 3 hours. Results of the research of phase composition of the reduction products, as well as chemical composition of the phases are considered. The possibility of selective solid-phase reduction of iron with solid carbon to the metallic state was confirmed. Iron in the studied conditions is reduced by carbon monoxide CO and passes into magnetic part. During the magnetic separation of the products of ore reduction roasting with solid carbon and carbon monoxide CO, the non-magnetic part contains oxides of manganese, silicon and calcium. The work results can be used in development of theoretical and technological foundations for the processing of ferromanganese ores, which are not processed by existing technologies.

Force balance in convectively driven dynamos with no inertia

We study dynamo action in rotating, plane layer Boussinesq convection in the absence of inertia. This allows a decomposition of the velocity into a thermal part driven by buoyancy, and a magnetic part driven by the Lorentz force. We have identified three families of solutions, defined in terms of what is the dominant contribution to the velocity. In weak field dynamos the dominant contribution is the thermal component, in super strong field dynamos the dominant contribution is magnetic and in strong field dynamos the two components are comparable. For each of these solutions we investigate the force balance in the momentum equation to determine the relative importance of the viscous, buoyancy, Coriolis and magnetic forces. We do this by extracting the solenoidal part of the individual terms in the momentum equation, thereby removing their pressure contributions. This is numerically preferable to the more common practice of taking the curl of the momentum equation, which introduces an extra derivative. We find that, irrespective of the type of dynamo solution, the dynamics is controlled by the horizontal forces (in projection). Furthermore, in the progression from weak to strong to super strong dynamos, we find that the viscous forces in the thermal equation become negligible, thereby leading to a balance between buoyancy and Coriolis forces. On the other hand, no corresponding trend is observed in the magnetic part of the momentum equation: the viscous stresses always remain significant. This can be attributed to the different degrees of smoothness of the Coriolis and Lorentz forces, the latter having contributions from strong, filamentary structures. We discuss how our findings relate to dynamo solutions in which viscosity plays no role whatsoever – so-called Taylor states.

Mineralogical characterisation and magnetic separation of vanadium-bearing converter slag

The recycling of metallic iron is commonly the first step to fully use the converter slag, which is the biggest waste discharge in the steelmaking process. This study presents a proposed improved process of separating metallic iron from vanadium-bearing converter slag more efficiently. The mineralogical and morphological characteristics of the converter slag were first investigated, and the results showed that most of the iron was incorporated in the spinel and olivine. Grinding, sieving and magnetic separation were combined to recover metallic iron from the converter slag, and yielded approximately 41.5% of iron in which the iron content was as high as 85%, and the non-magnetic concentrate contains 8.56% vanadium with a yield of 95.3% and 8.63% titanium with a yield of 85.3%. The magnetic part can be used as the raw materials in the steel making process, whereas the non-magnetic part can be used as the raw materials for the further extraction of vanadium.

The Weyl curvature tensor, Cotton–York tensor and gravitational waves: A covariant consideration

[Formula: see text] covariant approach to cosmological perturbation theory often employs the electric part ([Formula: see text]), the magnetic part ([Formula: see text]) of the Weyl tensor or the shear tensor ([Formula: see text]) in a phenomenological description of gravitational waves. The Cotton–York tensor is rarely mentioned in connection with gravitational waves in this approach. This tensor acts as a source for the magnetic part of the Weyl tensor which should not be neglected in studies of gravitational waves in the [Formula: see text] formalism. The tensor is only mentioned in connection with studies of “silent model” but even there the connection with gravitational waves is not exhaustively explored. In this study, we demonstrate that the Cotton–York tensor encodes contributions from both electric and magnetic parts of the Weyl tensor and in directly from the shear tensor. In our opinion, this makes the Cotton–York tensor arguably the natural choice for linear gravitational waves in the [Formula: see text] covariant formalism. The tensor is cumbersome to work with but that should negate its usefulness. It is conceivable that the tensor would equally be useful in the metric approach, although we have not demonstrated this in this study. We contend that the use of only one of the Weyl tensor or the shear tensor, although phenomenologically correct, leads to loss of information. Such information is vital particularly when examining the contribution of gravitational waves to the anisotropy of an almost-Friedmann–Lamitre–Robertson–Walker (FLRW) universe. The recourse to this loss is the use Cotton–York tensor.

Weyl compatible tensors

We introduce the new algebraic property of Weyl compatibility for symmetric tensors and vectors. It is strictly related to Riemann compatibility, which generalizes the Codazzi condition while preserving much of its geometric implications. In particular, it is shown that the existence of a Weyl compatible vector implies that the Weyl tensor is algebraically special, and it is a necessary and sufficient condition for the magnetic part to vanish. Some theorems (Derdziński and Shen [11], Hall [15]) are extended to the broader hypothesis of Weyl or Riemann compatibility. Weyl compatibility includes conditions that were investigated in the literature of general relativity (as in McIntosh et al. [16, 17]). A simple example of Weyl compatible tensor is the Ricci tensor of an hypersurface in a manifold with constant curvature.

Electromagnetically Induced Left-Handedness in a Dense Atomic Vapor Medium

We discuss how a three-level system can be used to change the frequency-dependent magnetic permeability of a dense atomic gas to be significantly different from 1. The results show that a negative permittivity and permeability simultaneously with transparent propagation of the electric part of the probe filed can be obtained. Moreover, the magnetic part of the probe field can be amplified instead of strong absorption as usual materials. Therefore, it may be possible to obtain left-handed electrodynamics for an atomic gas using three atomic levels.

Influence of Addition of Briquettes with Dust Content into the Charge of Electric Induction Furnace on Cast Iron Quality

Foundry dust from blasting and grinding of castings contain a high amount of iron, ergo it is possible its recycling in foundry process. Dust was compacted by briquetting, two kinds of briquettes were prepared (A contained 95% magnetic part of dust from casting blasting +5% bentonite and B contained 95% mixture of dust from casting grinding and magnetic part of dust from casting blasting + 5% bentonite) and used as a part of charge into the electric induction furnace. It was found that addition of briquettes has had an influence of a chemical composition of cast iron above all on content of sulphur, phosphorus and silicon. It was not reflected in decrease in tensile strength and in microstructure. Yield of metal from briquettes was not lower then 70%.