Collective excitations and low temperature transport properties of bismuth

We examine the influence of collective excitations on the transport properties (resistivity, magneto- optical conductivity) for semimetals, focusing on the case of bismuth. We show, using an RPA approximation, that the properties of the system are drastically affected by the presence of an acoustic plasmon mode, consequence of the presence of two types of carriers (electrons and holes) in this system. We found a crossover temperature T* separating two different regimes of transport. At high temperatures T > T* we show that Baber scattering explains quantitatively the DC resistivity experiments, while at low temperatures T < T* interactions of the carriers with this collective mode lead to a T^5 behavior of the resistivity. We examine other consequences of the presence of this mode, and in particular predict a two plasmon edge feature in the magneto-optical conductivity. We compare our results with the experimental findings on bismuth. We discuss the limitations and extensions of our results beyond the RPA approximation, and examine the case of other semimetals such as graphite or 1T-TiSe_2

On the Integrability and Chaos of an N=2 Maxwell-Chern-Simons-Higgs Mechanical Model

We apply different integrability analysis procedures to a reduced (spatially homogeneous) mechanical system derived from an off-shell non-minimally coupled N=2 Maxwell-Chern-Simons-Higgs model that presents BPS topological vortex excitations, numerically obtained with an ansatz adopted in a special - critical coupling - parametric regime. As a counterpart of the regularity associated to the static soliton-like solution, we investigate the possibility of chaotic dynamics in the evolution of the spatially homogeneous reduced system, descendant from the full N=2 model under consideration. The originally rich content of symmetries and interactions, N=2 susy and non-minimal coupling, singles out the proposed model as an interesting framework for the investigation of the role played by (super-)symmetries and parametric domains in the triggering/control of chaotic behavior in gauge systems. After writing down effective Lagrangian and Hamiltonian functions, and establishing the corresponding canonical Hamilton equations, we apply global integrability Noether point symmetries and Painleveproperty criteria to both the general and the critical coupling regimes. As a non-integrable character is detected by the pair of analytical criteria applied, we perform suitable numerical simulations, as we seek for chaotic patterns in the system evolution. Finally, we present some Comments on the results and perspectives for further investigations and forthcoming communications.Comment: 18 pages, 5 figure

Highly erosive glaciers on Mars - the role of water

International audiencePolewards of 30 • in each hemisphere, the surface of Mars hosts a suite of landforms reminiscent of glacial landscapes on Earth. Amongst these landforms are: 1) Viscous Flow Features (VFF), which resemble glaciers on Earth and are thought to contain large volumes of water ice, 2) martian gullies which are km-scale features resembling water-eroded gullies on Earth and 3) arcuate ridges thought to be moraines from previous glaciations. Gullies have been long-associated with a surface unit originally called "pasted-on terrain" and now often called the "latitude dependant mantle". Arcuate ridges are often found at the base of hillslopes with gullies, but are also found on hillslopes with pasted-on terrain and no gullies. We have found a systematic lowering of the slope of the bedrock exposure located topographically above the pasted-on terrain whether that same slope hosts gullies or not. The lowered bedrock exposures display a different surface texture from bedrock exposed on other parts of the crater wall and from fresh crater walls-it appears fragmented and has reduced relief. Using 1-m-digital elevation models from the High Resolution Imaging Science Experiment (HiRISE) we compared the slopes of eight "eroded" craters and seven unmodified craters. We estimated their age using the crater size-frequency distribution of small craters on their ejecta blankets. From this information we calculated bedrock retreat rates for the eroded craters and found they were up to ∼103 m Myr-1-equivalent to erosion rates of wet-based glaciers on Earth. This is several orders of magnitude higher than previous estimates of erosion by VFF (10-2-101 m Myr-1), which themselves are roughly equivalent to cold-based glaciers on Earth. Such erosion rates are sufficient to erase previously existing landforms, such as martian gullies. We hypothesise, therefore, that the pasted-on terrain is a glacial deposit, overturning its previous interpretation as an airfall deposit of ice nucleated on dust. We maintain the interpretation of the arcuate ridges as moraines, but further conclude that they are likely the result of glaciotectonic deformation of sub-marginal and proglacial sediment in the presence of sediment pore-water. We do not support the generation of large quantities of glacial meltwater because it would have broken-up and degraded the arcuate ridges and pasted-on terrain an produced a suite of landforms (e.g., hummocky moraine, lacustrine forms, outwash plains, eskers) which are not observed

A new twist to an old story: HE 0450-2958, and the ULIRG→\to (optically bright QSO) transition hypothesis

We report on interferometric imaging of the CO J=1--0 and J=3--2 line emission from the controversial QSO/galaxy pair HE 0450--2958. {\it The detected CO J=1--0 line emission is found associated with the disturbed companion galaxy not the luminous QSO,} and implies $\rm M_{gal}(H_2)\sim (1-2)\times 10^{10} M_{\odot}$, which is \ga 30% of the dynamical mass in its CO-luminous region. Fueled by this large gas reservoir this galaxy is the site of an intense starburst with $\rm SFR\sim 370 M_{\odot} yr^{-1}$, placing it firmly on the upper gas-rich/star-forming end of Ultra Luminous Infrared Galaxies (ULIRGs, $\rm L_{IR}>10^{12} L_{\odot}$). This makes HE 0450--2958 the first case of extreme starburst and powerful QSO activity, intimately linked (triggered by a strong interaction) but not coincident. The lack of CO emission towards the QSO itself renews the controversy regarding its host galaxy by making a gas-rich spiral (the typical host of Narrow Line Seyfert~1 AGNs) less likely. Finally, given that HE 0450--2958 and similar IR-warm QSOs are considered typical ULIRG$\to$(optically bright QSO) transition candidates, our results raise the possibility that some may simply be {\it gas-rich/gas-poor (e.g. spiral/elliptical) galaxy interactions} which ``activate'' an optically bright unobscured QSO in the gas-poor galaxy, and a starburst in the gas-rich one. We argue that such interactions may have gone largely unnoticed even in the local Universe because the combination of tools necessary to disentagle the progenitors (high resolution and S/N optical {\it and} CO imaging) became available only recently.Comment: 25 pages, 5 figures, accepted for publication by The Astrophysical Journa

Kondo temperature of magnetic impurities at surfaces

Based on the experimental observation, that only the close vicinity of a magnetic impurity at metal surfaces determines its Kondo behaviour, we introduce a simple model which explains the Kondo temperatures observed for cobalt adatoms at the (111) and (100) surfaces of Cu, Ag, and Au. Excellent agreement between the model and scanning tunneling spectroscopy (STS) experiments is demonstrated. The Kondo temperature is shown to depend on the occupation of the d-level determined by the hybridization between adatom and substrate with a minimum around single occupancy.Comment: 4 pages, 2 figure

“Зізнання авантюриста Фелікса Крулля” Томаса Манна як пародія на велику автобіографію

Статтю присвячено розгляду рецепції та відображення “Поезії і правди” Й.-В. Гете в романі Т. Манна “Зізнання авантюриста Фелікса Крулля”. Представлена розвідка продовжує ряд наукових досліджень, присвячених вивченню особливостей рецепції автобіографії Й.-В. Гете, зокрема в німецькомовному літературному просторі. При дослідженні особливостей наявного в аналізованому нами романі пародійного наслідування Й.-В. Гете основна увага зосереджується автором на його стилістичному та тематичному рівнях.Статья посвящена рассмотрению рецепции и отражения “Поэзии и правды” Й.-В. Гете в романе Т. Манна “Признания авантюриста Феликса Крулля”. Представленная статья продолжает ряд научных исследований, посвященных изучению особенностей рецепции автобиографии Й.-В. Гете в частности в немецкоязычном литературном пространстве. При изучении особенностей имеющихся в анализированном нами романе пародийного подражания Й.-В. Гете основное внимание автор сосредотачивает на его стилистическом и тематическом уровнях.The article focuses on the reception of Goethe’s “Poetry and Truth” and its reflection in T. Mann’s novel “The Confession of adventurer Felix Crool”. The given article extends the series of scientific investigations that deal with the peculiarities of Goethe’s reception in German literature. Studying the parody imitation peculiarities of Goethe in the analysed novel, the main attention is paid to the stylistic and theme levels

Interplay of size and Landau quantizations in the de Haas-van Alphen oscillations of metallic nanowires

We examine the interplay between size quantization and Landau quantization in the De Haas-Van Alphen oscillations of clean, metallic nanowires in a longitudinal magnetic field for `hard' boundary conditions, i.e. those of an infinite round well, as opposed to the `soft' parabolically confined boundary conditions previously treated in Alexandrov and Kabanov (Phys. Rev. Lett. {\bf 95}, 076601 (2005) (AK)). We find that there exist {\em two} fundamental frequencies as opposed to the one found in bulk systems and the three frequencies found by AK with soft boundary counditions. In addition, we find that the additional `magic resonances' of AK may be also observed in the infinite well case, though they are now damped. We also compare the numerically generated energy spectrum of the infinite well potential with that of our analytic approximation, and compare calculations of the oscillatory portions of the thermodynamic quantities for both models.Comment: Title changed, paper streamlined on suggestion of referrees, typos corrected, numerical error in figs 2 and 3 corrected and final result simplified -- two not three frequencies (as in the previous version) are observed. Abstract altered accordingly. Submitted to Physical Review

Valency of rare earths in RIn3 and RSn3: Ab initio analysis of electric-field gradients

In RIn3 and RSn3 the rare earth (R) is trivalent, except for Eu and Yb, which are divalent. This was experimentally determined in 1977 by perturbed angular correlation measurements of the electric-field gradient on a 111Cd impurity. At that time, the data were interpreted using a point charge model, which is now known to be unphysical and unreliable. This makes the valency determination potentially questionable. We revisit these data, and analyze them using ab initio calculations of the electric-field gradient. From these calculations, the physical mechanism that is responsible for the influence of the valency on the electric-field gradient is derived. A generally applicable scheme to interpret electric-field gradients is used, which in a transparent way correlates the size of the field gradient with chemical properties of the system.Comment: 10 page

Genomic selection: the option for new robustness traits?

Genomic selection is rapidly becoming the state-of-the-art genetic selection methodology in dairy cattle breeding schemes around the world. The objective of this paper was to explore possibilities to apply genomic selection for traits related to dairy cow robustness. Deterministic simulations indicate that replacing progeny testing with genomic selection may favour genetic response for production traits at the expense of robustness traits, owing to a disproportional change in accuracies obtained across trait groups. Nevertheless, several options are available to improve the accuracy of genomic selection for robustness traits. Moreover, genomic selection opens up the opportunity to begin selection for new traits using specialised reference populations of limited size where phenotyping of large populations of animals is currently prohibitive. Reference populations for such traits may be nucleus-type herds, research herds or pooled data from (international) research experiments or research herds. The RobustMilk project has set an example for the latter approach, by collating international data for progesterone-based traits, feed intake and energy balance-related traits. Reference population design, both in terms of relatedness of the animals and variability in phenotypic performance, is important to optimise the accuracy of genomic selection. Use of indicator traits, combined with multi-trait genomic prediction models, can further contribute to improved accuracy of genomic prediction for robustness traits. Experience to date indicates that for newly recorded robustness traits that are negatively correlated with the main breeding goal, cow reference populations of =10 000 are required when genotyping is based on medium- or high-density single-nucleotide polymorphism arrays. Further genotyping advances (e.g. sequencing) combined with post-genomics technologies will enhance the opportunities for (genomic) selection to improve cow robustness