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