Uniform approximation of homeomorphisms by diffeomorphisms

We prove that a compactly supported homeomorphism of a smooth manifold of dimension greater or equal to 5 can be approximated uniformly by compactly supported diffeomorphisms if and only if it is isotopic to a diffeomorphism. If the given homeomorphism is in addition volume preserving, then it can be approximated uniformly by volume preserving diffeomorphisms.Comment: v4: 5 pages; long overdue revision; clarified and improved statements, notation, and proofs. The main theorem may already be known, but I have not been able to find a precise reference. After talking to a number of topologists without getting a satisfactory answer, I decided to write up the proof myself. Comments and references welcom

Towards an understanding of hole superconductivity

From the very beginning K. Alex M\"uller emphasized that the materials he and George Bednorz discovered in 1986 were $hole$ superconductors. Here I would like to share with him and others what I believe to be $the$ key reason for why high $T_c$ cuprates as well as all other superconductors are hole superconductors, which I only came to understand a few months ago. This paper is dedicated to Alex M\"uller on the occasion of his 90th birthday.Comment: Dedicated to Alex M\"uller on the Occasion of his 90th Birthday. arXiv admin note: text overlap with arXiv:1703.0977

Centralized vs. Decentralized Wage Formation: The Role of Firms' Production Technology

This paper is the first to show theoretically and empirically how firms' production technology affects the choice of their preferred wage formation regime. Our theoretical framework predicts, first, that the larger the total factor productivity of a firm, the more likely it is to opt for centralized wage formation where it can hide behind less productive firms. Second, the larger a firm's scale elasticity, the higher its incentive to choose centralized rather than decentralized wage setting due to labor cost and straitjacket effects. As firms in Germany are allowed to choose their wage formation regime, we test these two hypotheses with representative establishment data for West Germany. We find that establishments with centralized bargaining agreements indeed have economically and statistically significantly larger total factor productivities and scale elasticities than comparable establishments outside the centralized bargaining regime

Centralized vs. decentralized wage formation: The role of firms' production technology

This paper is the first to show theoretically and empirically how firms' production technology affects the choice of their preferred wage formation regime. Our theoretical framework predicts, first, that the larger the total factor productivity of a firm, the more likely it is to opt for centralized wage formation where it can hide behind less productive firms. Second, the larger a firm's scale elasticity, the higher its incentive to choose centralized rather than decentralized wage setting due to labor cost and straitjacket effects. As firms in Germany are allowed to choose their wage formation regime, we test these two hypotheses with representative establishment data for West Germany. We find that establishments with centralized bargaining agreements indeed have economically and statistically significantly larger total factor productivities and scale elasticities than comparable establishments outside the centralized bargaining regime

Location tracking: views from the older adult population

Background: there has been a rise in the use of social media applications that allow people to see where friends, family and nearby services are located. Yet while uptake has been high for younger people, adoption by older adults is relatively slow, despite the potential health and social benefits. In this paper, we explore the barriers to acceptance of location-based services (LBS) in a community of older adults. Objective: to understand attitudes to LBS technologies in older adults. Methods: eighty-six older adults used LBS for 1-week and completed pre- and post-use questionnaires. Twenty available volunteers from the first study also completed in-depth interviews after their experience using the LBS technology. Results: the pre-use questionnaire identified perceptions of usefulness, individual privacy and visibility as predictive of intentions to use a location-tracking service. Post-use, perceived risk was the only factor to predict intention to use LBS. Interviews with participants revealed that LBS was primarily seen as an assistive technology and that issues of trust and privacy were important. Conclusion: the findings from this study suggest older adults struggle to see the benefits of LBS and have a number of privacy concerns likely to inhibit future uptake of location-tracking services and devices

Carpet Beater Molecules: Synthesis and Characterization of Functional Hexa‐peri‐benzocoronene–Alkyne Coupling Products

Abstract Within the scope of this paper, nine π‐expanded mono‐substituted 5,8,11,14,17‐pentakis‐(tert‐butyl)‐hexa‐peri‐hexabenzocoronenes (HBC) are introduced. 2‐Iodo‐5,8,11,14,17‐pentakis‐(tert‐butyl)‐hexa‐peri‐hexabenzocoronene served as precursor and was reacted with ethynyltrimethylsilane in a Sonogashira coupling reaction. The acetylene unit is used as a linker and can undergo another Sonogashira coupling reaction combining different phenyl coupling partners with the HBC core. The electron‐withdrawing groups such as nitrile, pyridine and carbonyl species (aldehyde, methylester, carboxylic acid) as well as the three quinoxaline based species (diphenylquinoxaline, dibenzo[a,c]phenazine, phenanthro[4’,5’‐a,b,c]phenazine) serve as substitution moieties. Their influence on the optoelectronic properties were investigated by UV/Vis absorption spectroscopy demonstrating a maximum redshift of 7 nm compared to starting compound 2‐Iodo‐5,8,11,14,17‐pentakis‐(tert‐butyl) HBC. As for the phenanthro[4’,5’‐a,b,c]phenazine substituted HBC a dramatic decrease in the intensity of the absorption of the UV/Vis spectrum was observed. The fluorescence spectroscopy pointed out that the dibenzo[a,c]phenazine and phenanthro[4’,5’‐a,b,c]phenazine substitution changed the spectra to one broad peak departing from the characteristic HBC‐like emission pattern

Computational Complexity of Iterated Maps on the Interval (Extended Abstract)

The exact computation of orbits of discrete dynamical systems on the interval is considered. Therefore, a multiple-precision floating point approach based on error analysis is chosen and a general algorithm is presented. The correctness of the algorithm is shown and the computational complexity is analyzed. As a main result, the computational complexity measure considered here is related to the Ljapunow exponent of the dynamical system under consideration

PLSDB: advancing a comprehensive database of bacterial plasmids

Plasmids are known to contain genes encoding for virulence factors and antibiotic resistance mechanisms. Their relevance in metagenomic data processing is steadily growing. However, with the increasing popularity and scale of metagenomics experiments, the number of reported plasmids is rapidly growing as well, amassing a considerable number of false positives due to undetected misassembles. Here, our previously published database PLSDB provides a reliable resource for researchers to quickly compare their sequences against selected and annotated previous findings. Within two years, the size of this resource has more than doubled from the initial 13,789 to now 34,513 entries over the course of eight regular data updates. For this update, we aggregated community feedback for major changes to the database featuring new analysis functionality as well as performance, quality, and accessibility improvements. New filtering steps, annotations, and preprocessing of existing records improve the quality of the provided data. Additionally, new features implemented in the web-server ease user interaction and allow for a deeper understanding of custom uploaded sequences, by visualizing similarity information. Lastly, an application programming interface was implemented along with a python library, to allow remote database queries in automated workflows. The latest release of PLSDB is freely accessible under https://www.ccb.uni-saarland.de/plsdb

Ferromagnetism in the Hubbard model: instability of the Nagaoka state on the triangular, honeycomb and kagome lattices

In order to analyse the lattice dependence of ferromagnetism in the two-dimensional Hubbard model we investigate the instability of the fully polarized ferromagnetic ground state (Nagaoka state) on the triangular, honeycomb and kagome lattices. We mainly focus on the local instability, applying single spin flip variational wave functions which include majority spin correlation effects. The question of global instability and phase separation is addressed in the framework of Hartree-Fock theory. We find a strong tendency towards Nagaoka ferromagnetism on the non-bipartite lattices (triangular, kagome) for more than half filling. For the triangular lattice we find the Nagaoka state to be unstable above a critical density of $n=1.887$ at $U=\infty$, thereby significantly improving former variational results. For the kagome lattice the region where ferromagnetism prevails in the phase diagram widely exceeds the flat band regime. Our results even allow the stability of the Nagaoka state in a small region below half filling. In the case of the bipartite honeycomb lattice several disconnected regions are left for a possible Nagaoka ground state.Comment: 31 pages + 11 figures, submitted as uuencoded compressed ps-file, to be published in Annalen der Physi