Asymmetric field dependence of magnetoresistance in magnetic films

We study an asymmetric in field magnetoresistance that is frequently observed in magnetic films and, in particular, the odd longitudinal voltage peaks that appear during magnetization reversal in ferromagnetic films, with out-of-plane magnetic anisotropy. We argue that the anomalous signals result from small variation of magnetization and Hall resistivity along the sample. Experimental data can be well described by a simple circuit model, the latter being supported by analytic and numerical calculations of current and electric field distribution in films with a gradual variation of the magnetization and Hall resistance.Comment: 7 pages, 5 figures, to be published in Phys. Rev.

Magnetization driven metal - insulator transition in strongly disordered Ge:Mn magnetic semiconductors

We report on the temperature and field driven metal-insulator transition in disordered Ge:Mn magnetic semiconductors accompanied by magnetic ordering, magnetoresistance reaching thousands of percents and suppression of the extraordinary Hall effect by a magnetic field. Magnetoresistance isotherms are shown to obey a universal scaling law with a single scaling parameter depending on temperature and fabrication. We argue that the strong magnetic disorder leads to localization of charge carriers and is the origin of the unusual properties of Ge:Mn alloys.Comment: 10 pages, 5 figure

Topology in the 2d Heisenberg Model under Gradient Flow

The 2d Heisenberg model --- or 2d O(3) model --- is popular in condensed matter physics, and in particle physics as a toy model for QCD. Along with other analogies, it shares with 4d Yang-Mills theories, and with QCD, the property that the configurations are divided in topological sectors. In the lattice regularisation the topological charge $Q$ can still be defined such that $Q \in \mathbb{Z}$. It has generally been observed, however, that the topological susceptibility $\chi_{\rm t} = \langle Q^2 \rangle / V$ does not scale properly in the continuum limit, i.e. that the quantity $\chi_{\rm t} \xi^2$ diverges for $\xi \to \infty$ (where $\xi$ is the correlation length in lattice units). Here we address the question whether or not this divergence persists after the application of the Gradient Flow.Comment: 10 pages, LaTex, 7 figures, 2 tables, talk presented at the XXXI Reuni\'on Anual de la Divisi\'on de Part\'iculas y Campos de la Sociedad Mexicana de F\'isica (CINVESTAV, Mexico City

The MUCHFUSS photometric campaign

Hot subdwarfs (sdO/Bs) are the helium-burning cores of red giants, which lost almost all of their hydrogen envelopes. This mass loss is often triggered by common envelope interactions with close stellar or even substellar companions. Cool companions like late-type stars or brown dwarfs are detectable via characteristic light curve variations like reflection effects and often also eclipses. To search for such objects we obtained multi-band light curves of 26 close sdO/B binary candidates from the MUCHFUSS project with the BUSCA instrument. We discovered a new eclipsing reflection effect system ($P=0.168938$~d) with a low-mass M dwarf companion ($0.116 M_{\rm \odot}$). Three more reflection effect binaries found in the course of the campaign were already published, two of them are eclipsing systems, in one system only showing the reflection effect but no eclipses the sdB primary is found to be pulsating. Amongst the targets without reflection effect a new long-period sdB pulsator was discovered and irregular light variations were found in two sdO stars. The found light variations allowed us to constrain the fraction of reflection effect binaries and the substellar companion fraction around sdB stars. The minimum fraction of reflection effect systems amongst the close sdB binaries might be greater than 15\% and the fraction of close substellar companions in sdB binaries might be as high as $8.0\%$. This would result in a close substellar companion fraction to sdB stars of about 3\%. This fraction is much higher than the fraction of brown dwarfs around possible progenitor systems, which are solar-type stars with substellar companions around 1 AU, as well as close binary white dwarfs with brown dwarf companions. This might be a hint that common envelope interactions with substellar objects are preferentially followed by a hot subdwarf phase.Comment: accepted for A&

Low temperature relation for the trace of the energy-momentum tensor in QCD with light quarks

It is shown that the temperature derivatives of the anomalous and normal (quark massive term) contributions to the trace of the energy-momentum tensor in QCD are equal to each other in the low temperature region. The physical consequences of this relation are discussed.Comment: RevTeX, 4 pages, no figure

Pressure-Induced Rotational Symmetry Breaking in URu2_2Si2_2

Phase transitions and symmetry are intimately linked. Melting of ice, for example, restores translation invariance. The mysterious hidden order (HO) phase of URu$_2$Si$_2$ has, despite relentless research efforts, kept its symmetry breaking element intangible. Here we present a high-resolution x-ray diffraction study of the URu$_2$Si$_2$ crystal structure as a function of hydrostatic pressure. Below a critical pressure threshold $p_c\approx3$ kbar, no tetragonal lattice symmetry breaking is observed even below the HO transition $T_{HO}=17.5$ K. For $p>p_c$, however, a pressure-induced rotational symmetry breaking is identified with an onset temperatures $T_{OR}\sim 100$ K. The emergence of an orthorhombic phase is found and discussed in terms of an electronic nematic order that appears unrelated to the HO, but with possible relevance for the pressure-induced antiferromagnetic (AF) phase. Existing theories describe the HO and AF phases through an adiabatic continuity of a complex order parameter. Since none of these theories predicts a pressure-induced nematic order, our finding adds an additional symmetry breaking element to this long-standing problem.Comment: 6 pages, 4 figures and supplemental material

Importance of maintained atrio-ventricular synchrony in patients with pacemarkers

The effect of atrial contraction on cardiac function is reviewed in patients with dual chamber and rate-responsive ventricular pacemakers. The question posed was is there any haemodynamic, clinical or prognostic advantage of AV synchrony in dual chamber pacemakers in comparison to rate-responsive ventricular pacemakers? Optimal A V delay in dual chamber pacing favours cardiac performance at rest, while during exercise the increase in heart rate rather than A V synchrony influences cardiac performance and working capacity. However, there is little information on the benefit of maintained A V synchrony in patients' daily activities. Patients with pacemakers which maintain AV synchrony seem to have less morbidity and mortality than patients with ventricular stimulation alone, and there are comparable rates of complication in carriers of single and dual chamber pacemakers, the former showing problems with the pacemaker syndrome and the latter with atrial sensing and pacemaker-induced tachycardias. The disadvantage of dual chamber pacemakers are higher costs and time-consuming control

Quality is in the eye of the stakeholders: what do professional subtitlers and viewers think about subtitling?

Quality is a rather slippery concept, and its assessment in subtitling can be a challenging task, as its appreciation can easily vary depending on the diferent stakeholders involved in the production and reception of subtitles. In this paper, we evaluate quality indicators in subtitling as perceived by professional subtitlers and viewers. After exploring the various subtitle parameters that can have an impact on the quality of the end product (such as line breaks, synchronisation, display rates), we present the results of two qualitative studies conducted with professional subtitlers and subtitle viewers with diferent audiovisual backgrounds. The results yield some similarities and discrepancies, particularly in the way in which the strategy of condensation is perceived by the two groups, and they also help delineate the subtitle parameters that should be taken into consideration in order to improve the creative process as well as the reception of subtitles