9,089 research outputs found
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 can still be defined such
that . It has generally been observed, however, that the
topological susceptibility does not
scale properly in the continuum limit, i.e. that the quantity diverges for (where 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
Teaching Law Students about Sexual Orientation, Gender Identity and Intersex Status within Human Rights Law: Seven Principles for Curriculum Design and Pedagogy
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
(~d) with a low-mass M dwarf companion ().
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 . 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 URuSi
Phase transitions and symmetry are intimately linked. Melting of ice, for
example, restores translation invariance. The mysterious hidden order (HO)
phase of URuSi has, despite relentless research efforts, kept its
symmetry breaking element intangible. Here we present a high-resolution x-ray
diffraction study of the URuSi crystal structure as a function of
hydrostatic pressure. Below a critical pressure threshold kbar,
no tetragonal lattice symmetry breaking is observed even below the HO
transition K. For , however, a pressure-induced rotational
symmetry breaking is identified with an onset temperatures 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
- …