1,053 research outputs found
New Developments in FormCalc 8.4
We present new developments in FeynArts 3.9 and FormCalc 8.4, in particular
the MSSMCT model file including the complete one-loop renormalization,
vectorization/parallelization issues, and the interface to the Ninja library
for tensor reduction.Comment: 7 pages, proceedings contribution to Loops & Legs 2014, April 27-May
2, 2014, Weimar, German
The Active Audience? Gurus, Management Ideas and Consumer Variability
This study draws on an active audience perspective to develop a better understanding of mass audiences' attraction towards popular management ideas. It focuses on audience members' own experiences and, in particular, what audience activities actually play a role in shaping mass attraction, and how the deployment of these activities may vary. Analysing 65 in-depth interviews with management practitioners in their role as audience members of guru seminars, the authors identify different key consumption activities, and explain how individual management practitioners may shift in consumption orientation throughout the communication process. This paper argues that such a broader and more dynamic understanding of consumption activity is essential in understanding the success and impact of management ideas, and opens several fruitful research directions
Time-resolved observation of spin-charge deconfinement in fermionic Hubbard chains
Elementary particles such as the electron carry several quantum numbers, for
example, charge and spin. However, in an ensemble of strongly interacting
particles, the emerging degrees of freedom can fundamentally differ from those
of the individual constituents. Paradigmatic examples of this phenomenon are
one-dimensional systems described by independent quasiparticles carrying either
spin (spinon) or charge (holon). Here we report on the dynamical deconfinement
of spin and charge excitations in real space following the removal of a
particle in Fermi-Hubbard chains of ultracold atoms. Using space- and
time-resolved quantum gas microscopy, we track the evolution of the excitations
through their signatures in spin and charge correlations. By evaluating
multi-point correlators, we quantify the spatial separation of the excitations
in the context of fractionalization into single spinons and holons at finite
temperatures
A subradiant optical mirror formed by a single structured atomic layer
Efficient and versatile interfaces for the interaction of light with matter
are an essential cornerstone for quantum science. A fundamentally new avenue of
controlling light-matter interactions has been recently proposed based on the
rich interplay of photon-mediated dipole-dipole interactions in structured
subwavelength arrays of quantum emitters. Here we report on the direct
observation of the cooperative subradiant response of a two-dimensional (2d)
square array of atoms in an optical lattice. We observe a spectral narrowing of
the collective atomic response well below the quantum-limited decay of
individual atoms into free space. Through spatially resolved spectroscopic
measurements, we show that the array acts as an efficient mirror formed by only
a single monolayer of a few hundred atoms. By tuning the atom density in the
array and by changing the ordering of the particles, we are able to control the
cooperative response of the array and elucidate the interplay of spatial order
and dipolar interactions for the collective properties of the ensemble. Bloch
oscillations of the atoms out of the array enable us to dynamically control the
reflectivity of the atomic mirror. Our work demonstrates efficient optical
metamaterial engineering based on structured ensembles of atoms and paves the
way towards the controlled many-body physics with light and novel light-matter
interfaces at the single quantum level.Comment: 8 pages, 5 figures + 12 pages Supplementary Infomatio
Density-functional theory investigation of oxygen adsorption at Pd(11N)(N=3,5,7) vicinal surfaces
We present a density-functional theory study addressing the on-surface
adsorption of oxygen at the Pd(11N) (N =3,5,7) vicinal surfaces, which exhibit
(111) steps and (100) terraces of increasing width. We find the binding to be
predominantly governed by the local coordination at the adsorption site. This
leads to very similar bonding properties at the threefold step sites of all
three vicinal surfaces, while the binding at the central fourfold hollow site
in the four atomic row terrace of Pd(117) is already very little disturbed by
the presence of the neighboring steps.Comment: 9 pages including 4 figures; related publications can be found at
http://www.fhi-berlin.mpg.de/th/th.htm
Bringing Out-of-School Learning into the Classroom : Self- versus Peer-Monitoring of Learning Behaviour
Based on classroom management fostering autonomy support and intrinsic motivation, this study examines effects of reciprocal peer-monitoring of learning behaviours on cognitive and affective outcomes. Within our study, 470 German secondary school students between 13 and 16 years of age participated in a multimodal hands- and minds-on exhibition focusing on renewable resources. Three groups were separated and monitored via a pre-post-follow up questionnaire: the first conducted peer-monitoring with the performance of specific roles to manage students’ learning behaviours, the second accomplished a self-monitoring strategy, while the third group did not visit the exhibition. In contrast to the latter control group, both treatment groups produced a high increase in short- and long-term knowledge achievement. The peer-monitored group scored higher in cognitive learning outcomes than the self-monitored group did. Interestingly, the perceived level of choice did not differ between both treatment groups, whereas peer-monitoring increased students’ perceived competence and simultaneously reduced the perceived level of anxiety and boredom. Peer-monitoring realised with the performance of specific roles seems to keep students “on task” without lowering indicators for students’ intrinsic motivation. Herewith, we are amongst the first to suggest peer-monitoring as a semi-formal learning approach to balance between teacher-controlled instruction and free-choice exploration
DOES “THINKING IN SYSTEMS” FOSTER A CROSSDISCIPLINARY UNDERSTANDING OF ENERGY?
In school education the concept of energy should be a unifying element between all natural science disciplines. Still, many characteristics of living systems appear to be in contradiction to the laws of physics. Physics often refer to energy conservation in a closed system, whereas biology is often dominated by open ecological or physiological systems with a "dynamic equilibrium“. This makes the underlying, crosscutting scientific concept of energy hard to understand. Our study investigated if the idea of an open energy system (with an in- and output of energy), located within an “idealized” closed system (in which the total amount of energy is conserved), offers the potential for a cross-disciplinary understanding. We developed a learning environment and applied interviews to identify students’ ability to think in open and closed systems. Four teaching experiments with focus groups of three students each (9th grade, secondary school, males = 10) were carried out. Within the learning environment a scaled model illustrated the idea of an open system that is in direct exchange with the environment (representing an “idealized” closed system). We identified specific learning obstacles that are connected with energy conservation within the closed system, where students faced severe difficulties to detect the conversion of energy within the environment. A molecular perspective could “rebuild” the visibility and tangibility of energetic processes. We propose the particle model to bridge the apparent macroscopic – molecular gap
Floquet Prethermalization in a Bose-Hubbard System
Periodic driving has emerged as a powerful tool in the quest to engineer new
and exotic quantum phases. While driven many-body systems are generically
expected to absorb energy indefinitely and reach an infinite-temperature state,
the rate of heating can be exponentially suppressed when the drive frequency is
large compared to the local energy scales of the system -- leading to
long-lived 'prethermal' regimes. In this work, we experimentally study a
bosonic cloud of ultracold atoms in a driven optical lattice and identify such
a prethermal regime in the Bose-Hubbard model. By measuring the energy
absorption of the cloud as the driving frequency is increased, we observe an
exponential-in-frequency reduction of the heating rate persisting over more
than 2 orders of magnitude. The tunability of the lattice potentials allows us
to explore one- and two-dimensional systems in a range of different interacting
regimes. Alongside the exponential decrease, the dependence of the heating rate
on the frequency displays features characteristic of the phase diagram of the
Bose-Hubbard model, whose understanding is additionally supported by numerical
simulations in one dimension. Our results show experimental evidence of the
phenomenon of Floquet prethermalization, and provide insight into the
characterization of heating for driven bosonic systems
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