Gravitationally dressed Parke-Taylor amplitudes

A generating function for the Parke-Taylor amplitudes with any number of positive helicity gravitons in addition to the positive helicity gluons is obtained using the recently constructed self-dual classical solution of the type of perturbiner in Yang-Mills theory interacting with gravity.Comment: 4 pages, Late

Composite S-Brane Solutions On Product Of Ricci-Flat Spaces

A family of generalized $S$-brane solutions with orthogonal intersection rules and $n$ Ricci-flat factor spaces in the theory with several scalar fields and antisymmetric forms is considered. Two subclasses of solutions with power-law and exponential behaviour of scale factors are singled out. These subclasses contain sub-families of solutions with accelerated expansion of certain factor spaces. The solutions depend on charge densities of branes, their dimensions and intersections, dilatonic couplings and the number of dilatonic fields.Comment: To appear in GR

On the Interpretation of the Redshift in a Static Gravitational Field

The classical phenomenon of the redshift of light in a static gravitational potential, usually called the gravitational redshift, is described in the literature essentially in two ways: on the one hand the phenomenon is explained through the behaviour of clocks which run the faster the higher they are located in the potential, whereas the energy and frequency of the propagating photon do not change with height. The light thus appears to be redshifted relative to the frequency of the clock. On the other hand the phenomenon is alternatively discussed (even in some authoritative texts) in terms of an energy loss of a photon as it overcomes the gravitational attraction of the massive body. This second approach operates with notions such as the "gravitational mass" or the "potential energy" of a photon and we assert that it is misleading. We do not claim to present any original ideas or to give a comprehensive review of the subject, our goal being essentially a pedagogical one.Comment: latex, 16 pages, to be published in American Journal of Physic

Gas gain on single wire chambers filled with pure isobutane at low pressure

The gas gain of single-wire chambers filled with isobutane, with cell cross-section 12x12 mm and wire diameters of 15, 25, 50 and 100 $\mu$m, has been measured at pressures ranging 12-92 Torr. Contrary to the experience at atmospheric pressure, at very low pressures the gas gain on thick wires is higher than that on thin wires at the same applied high voltage as was recently shown. Bigger wire diameters should be used in wire chambers operating at very low pressure if multiple scattering on wires is not an issue.Comment: 9 pages, 6 figure

Prospects for the Ferronickel Production Development from the Urals Oxidized Nickel Ores

Methods of ore processing are divided into hydro- and pyrometallurgical. The latter method is more common. Ferronickel is seeing high demand at present. It is produced by reducing electric smelting of previously calcined ore. This method is typically used because of the composition and quality of the products obtained (there is a particularly large market for Ferronickel of the standard ISO 6501:1988, containing at least 15% Ni). Processing technologies for converting poor oxidized nickel ores into ferronickel offer significant advantages, reducing the environmental impact and energy consumption, and increase the recovery of valuable metals. This study considers the processing technology of serpentinite ores, which includes: ore preparation (averaging, crushing and screening, drying); roasting a mixture of dried ore and crushed dolomite (flux) in tubular rotary kilns; melting of hot cinder with the addition of a reducing agent in an ore-smelting direct-current electric furnace to produce a rough ferronickel; refining ferronickel from impurities of carbon, silicon, sulfur, phosphorus, chromium was substantiated. During the industrial testing of electric smelting of calcined ores from the Ural deposits, ferronickel, containing (in wt. %) 8.9-15.5 Ni, 1.1 Cr, 0.17 Co, 0.1 S, 0.1 C was produced. Nickel extraction in ferronickel was 96.1 %, cobalt – 89.1 %. Keywords: ore, nickel, production, heating, roasting and reduction, phase transition

Extending Wadge theory to k-partitions

© Springer International Publishing AG 2017. We extend some results about Wadge degrees of Borel subsets of Baire space to finite partitions of Baire space. A typical new result is the characterization up to isomorphism of the Wadge degrees of k-partitions with Δ 0 3 -components