The classical double copy for Taub-NUT spacetime

The double copy is a much-studied relationship between gauge theory and gravity amplitudes. Recently, this was generalised to an infinite family of classical solutions to Einstein's equations, namely stationary Kerr-Schild geometries. In this paper, we extend this to the Taub-NUT solution in gravity, which has a double Kerr-Schild form. The single copy of this solution is a dyon, whose electric and magnetic charges are related to the mass and NUT charge in the gravity theory. Finally, we find hints that the classical double copy extends to curved background geometries.Comment: 13 pages, no figures. Minor edits to match journal versio

Spherical orbit closures in simple projective spaces and their normalizations

Let G be a simply connected semisimple algebraic group over an algebraically closed field k of characteristic 0 and let V be a rational simple G-module of finite dimension. If G/H \subset P(V) is a spherical orbit and if X is its closure, then we describe the orbits of X and those of its normalization. If moreover the wonderful completion of G/H is strict, then we give necessary and sufficient combinatorial conditions so that the normalization morphism is a homeomorphism. Such conditions are trivially fulfilled if G is simply laced or if H is a symmetric subgroup.Comment: 24 pages, LaTeX. v4: Final version, to appear in Transformation Groups. Simplified some proofs and corrected minor mistakes, added references. v3: major changes due to a mistake in previous version

Study of a colliding laser-produced plasma by analysis of time and space-resolved image spectra

The interaction of two counter-propagating laser-produced plasmas was studied using simultaneous imaging and spectroscopic techniques. Spectrally-filtered time-gated ICCD imaging was used to obtain information about the spatial dynamics and temporal evolution of the collision process. While, time-resolved imaging spectroscopy was used to determine the spatial and temporal distributions of electron temperature and density within the interaction region. We examine specifically the interaction of plasmas whose parameters match those typically used in pulsed laser deposition of thin films. These low temperature plasmas are highly collisional leading to the creation of a pronounced stagnation layer in the interaction region

Massive young stellar object W42-MME: The discovery of an infrared jet using VLT/NACO near-infrared images

We report on the discovery of an infrared jet from a deeply embedded infrared counterpart of 6.7 GHz methanol maser emission (MME) in W42 (i.e. W42-MME). We also investigate that W42-MME drives a parsec-scale H2 outflow, with detection of bow shock feature at ~0.52 pc to the north. The inner ~0.4 pc part of the H2 outflow has a position angle of ~18 deg and the position angle of ~40 deg is found farther away on either side of outflow from W42-MME. W42-MME is detected at wavelengths longer than 2.2 microns and is a massive young stellar object, with the estimated stellar mass of 19+-4 Msun. We map the inner circumstellar environment of W42-MME using VLT/NACO adaptive optics Ks and L' observations at resolutions ~0.2 arcsec and ~0.1 arcsec, respectively. We discover a collimated jet in the inner 4500 AU using the L' band, which contains prominent Br alpha line emission. The jet is located inside an envelope/cavity (extent ~10640 AU) that is tapered at both ends and is oriented along the north-south direction. Such observed morphology of outflow cavity around massive star is scarcely known and is very crucial for understanding the jet-outflow formation process in massive star formation. Along the flow axis, which is parallel to the previously known magnetic field, two blobs are found in both the NACO images at distances of ~11800 AU, located symmetrically from W42-MME. The observed W42-MME jet-outflow configuration can be used to constrain the jet launching and jet collimation models in massive star formation.Comment: 6 pages, 5 figures, Accepted for publication in The Astrophysical Journa

Effects of four Fusarium toxins (fumonisin B(1), alpha-zearalenol, nivalenol and deoxynivalenol) on porcine whole-blood cellular proliferation.

The in vitro effects of four Fusarium toxins, fumonisin B1 (FB1), a-zearalenol (a-ZEA), nivalenol (NIV) and deoxynivalenol (DON), on mitogen-induced cell proliferation were determined in swine whole-blood cultures. Considering the lack of sufficient toxicological data both on single and in combination effects, in vitro studies may contribute to risk assessment of these toxins. Incubation with increasing concentrations of FB1 did not produce any consequence on proliferation; in contrast a-ZEA, NIV and DON showed an inhibitory effect. Dose–response curves for each mycotoxin were generated. NIV was found to be the most potent toxin followed by DON and a-ZEA. The effects of both FB1 þ a-ZEA and NIVþ DON mixtures were also analysed to investigate possible interactions. The results indicated that combination of FB1þ a-ZEA produces a synergistic inhibition of porcine cell proliferation; whereas there is no interaction between DON and NIV on porcine wholeblood proliferation, at tested concentrations

Formal deduction of the Saint-Venant-Exner model including arbitrarily sloping sediment beds and associated energy

In this work we present a deduction of the Saint-Venant-Exner model through an asymptotic analysis of the Navier-Stokes equations. A multi-scale analysis is performed in order to take into account that the velocity of the sediment layer is smaller than the one of the fluid layer. This leads us to consider a shallow water type system for the fluid layer and a lubrication Reynolds equation for the sediment one. This deduction provides some improvements with respect to the classical Saint-Venant-Exner model: (i) the deduced model has an associated energy. Moreover, it allows us to explain why classical models do not have an associated energy and how to modify them in order to recover a model with this property. (ii) The model incorporates naturally a necessary modification that must be taken into account in order to be applied to arbitrarily sloping beds. Furthermore, we show that this modification is different of the ones considered classically, and that it coincides with a classical one only if the solution has a constant free surface. (iii) The deduced solid transport discharge naturally depends on the thickness of the moving sediment layer, what allows to ensure sediment mass conservation. Moreover, we include a simplified version of the model for the case of quasi-stationary regimes. Some of these simplified models correspond to the generalization of classical ones such as Meyer-Peter$\&$M\"uller and Ashida-Michiue models. Three numerical tests are presented to study the evolution of a dune for several definition of the repose angle, to see the influence of the proposed definition of the effective shear stress in comparison with the classical one, and by comparing with experimental data.Comment: 44 pages, sumbitted to Advances in Water Resources 17 july 201