1,392 research outputs found
A new interpretation of dielectric data in molecular glass formers
Literature dielectric data of glycerol, propylene carbonate and
ortho-terphenyl (OTP) show that the measured dielectric relaxation is a decade
faster than the Debye expectation, but still a decade slower than the breakdown
of the shear modulus. From a comparison of time scales, the dielectric
relaxation seems to be due to a process which relaxes not only the molecular
orientation, but the entropy, the short-range order and the density as well. On
the basis of this finding, we propose an alternative to the
Gemant-DiMarzio-Bishop extension of the Debye picture.Comment: 7 pages, 4 figures, 68 references; 3. version extended following
referee advic
Crystal structure, incommensurate magnetic order and ferroelectricity in mncuwo (x=0-0.19)
We have carried out a systematic study on the effect of Cu doping on nuclear,
magnetic, and dielectric properties in MnCuWO for
by a synergic use of different techniques, viz, heat
capacity, magnetization, dielectric, and neutron powder diffraction
measurements. Via heat capacity and magnetization measurements we show that
with increasing Cu concentration magnetic frustration decreases, which leads to
the stabilization of commensurate magnetic ordering. This was further verified
by temperature-dependent unit cell volume changes derived from neutron
diffraction measurements which was modeled by the Gr\"{u}neisen approximation.
Dielectric measurements show a low temperature phase transition below about
9-10 K. Further more, magnetic refinements reveal no changes below this
transition indicating a possible spin-flop transition which is unique to the Cu
doped system. From these combined studies we have constructed a magnetoelectric
phase diagram of this compound.Comment: 9 pages, 9 figures, accepted for publication in PR
Minimal Gauge Invariant Classes of Tree Diagrams in Gauge Theories
We describe the explicit construction of groves, the smallest gauge invariant
classes of tree Feynman diagrams in gauge theories. The construction is valid
for gauge theories with any number of group factors which may be mixed. It
requires no summation over a complete gauge group multiplet of external matter
fields. The method is therefore suitable for defining gauge invariant classes
of Feynman diagrams for processes with many observed final state particles in
the standard model and its extensions.Comment: 13 pages, RevTeX (EPS figures
Supporting active database learning and training through interactive multimedia
The learning objectives of a database course include aspects from conceptual and theoretical knowledge to practical development and implementation skills. We present an interactive educational multimedia system based on the virtual apprenticeship model for the knowledge- and skills-oriented Web-based education of database course students. Combining knowledge learning and skills training in an integrated environment is a central aspect of our system. We show that tool-mediated independent learning and training in an authentic setting is an alternative to traditional classroom-based approaches
Modern Particle Physics Event Generation with WHIZARD
We describe the multi-purpose Monte-Carlo event generator WHIZARD for the
simulation of high-energy particle physics experiments. Besides the
presentation of the general features of the program like SM physics, BSM
physics, and QCD effects, special emphasis will be given to the support of the
most accurate simulation of the collider environments at hadron colliders and
especially at future linear lepton colliders. On the more technical side, the
very recent code refactoring towards a completely object-oriented software
package to improve maintainability, flexibility and code development will be
discussed. Finally, we present ongoing work and future plans regarding
higher-order corrections, more general model support including the setup to
search for new physics in vector boson scattering at the LHC, as well as
several lines of performance improvements.Comment: 7 pages; contribution to the proceedings of the conference "ACAT 2014
(Advanced Computing and Analysis Techniques in physics)", Prague, Czech
Republic, September 201
Algebraic approach to quantum field theory on a class of noncommutative curved spacetimes
In this article we study the quantization of a free real scalar field on a
class of noncommutative manifolds, obtained via formal deformation quantization
using triangular Drinfel'd twists. We construct deformed quadratic action
functionals and compute the corresponding equation of motion operators. The
Green's operators and the fundamental solution of the deformed equation of
motion are obtained in terms of formal power series. It is shown that, using
the deformed fundamental solution, we can define deformed *-algebras of field
observables, which in general depend on the spacetime deformation parameter.
This dependence is absent in the special case of Killing deformations, which
include in particular the Moyal-Weyl deformation of the Minkowski spacetime.Comment: LaTeX 14 pages, no figures, svjour3.cls style; v2: clarifications and
references added, compatible with published versio
Nanometer-Resolved Collective Micromeniscus Oscillations through Optical Diffraction
We study the dynamics of periodic arrays of micrometer-sized liquid-gas
menisci formed at superhydrophobic surfaces immersed into water. By measuring
the intensity of optical diffraction peaks in real time we are able to resolve
nanometer scale oscillations of the menisci with sub-microsecond time
resolution. Upon driving the system with an ultrasound field at variable
frequency we observe a pronounced resonance at a few hundred kHz, depending on
the exact geometry. Modeling the system using the unsteady Stokes equation, we
find that this low resonance frequency is caused by a collective mode of the
acoustically coupled oscillating menisci.Comment: 4 pages, 5 figure
A Completely Invariant SUSY Transform of Supersymmetric QED
We study the SUSY breaking of the covariant gauge-fixing term in SUSY QED and
observe that this corresponds to a breaking of the Lorentz gauge condition by
SUSY. Reasoning by analogy with SUSY's violation of the Wess-Zumino gauge, we
argue that the SUSY transformation, already modified to preserve Wess-Zumino
gauge, should be further modified by another gauge transformation which
restores the Lorentz gauge condition. We derive this modification and use the
resulting transformation to derive a Ward identitiy relating the photon and
photino propagators without using ghost fields. Our transformation also
fulfills the SUSY algebra, modulo terms that vanish in Lorentz gauge
Magnetic neutron scattering study of YVO3: Evidence for an orbital Peierls state
Neutron spectroscopy has revealed a highly unusual magnetic structure and
dynamics in YVO, an insulating pseudocubic perovskite that undergoes a
series of temperature induced phase transitions between states with different
spin and orbital ordering patterns. A good description of the neutron data is
obtained by a theoretical analysis of the spin and orbital correlations of a
realistic one-dimensional model. This leads to the tentative identification of
one of the phases of YVO with the ``orbital Peierls state'', a
theoretically proposed many-body state comprised of orbital singlet bonds.Comment: final version, to appear in PR
Hai Karate and Kung Fuey: Early Martial Arts Tropes in British Advertising
This paper focuses on the responsibility of advertising messages to authentically mirror and reflect British audience feelings towards ‘the Other’ and discusses caricatures of the Chinese in advertising through early martial arts tropes. It provides contextual background to Chinese depictions on screen in Britain before illustrating martial arts representations on print and television advertising during the 1970s. The paper includes examples of two popular brands in Britain: Pfizer’s ‘Hai Karate’ (1973) and Golden Wonder’s ‘Kung Fuey’ (1974-76) to illustrate colonial notions of the ‘Oriental’ during the 1960s and ’70s. This interdisciplinary study borrows from ethical representation and martial arts discourse in film and TV, to explain the exoticisation and exclusion of the Chinese in the context of authenticity and appropriation in advertising
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