The Cuba Library

Concepts and implementation of the Cuba library for multidimensional numerical integration are elucidated.Comment: 6 pages. Talk given at the X International Workshop on Advanced Computing and Analysis Techniques in Physics Research, ACAT 2005, DESY-Zeuthen, Germany, 22-27 May 200

On the efficient numerical solution of lattice systems with low-order couplings

We apply the Quasi Monte Carlo (QMC) and recursive numerical integration methods to evaluate the Euclidean, discretized time path-integral for the quantum mechanical anharmonic oscillator and a topological quantum mechanical rotor model. For the anharmonic oscillator both methods outperform standard Markov Chain Monte Carlo methods and show a significantly improved error scaling. For the quantum mechanical rotor we could, however, not find a successful way employing QMC. On the other hand, the recursive numerical integration method works extremely well for this model and shows an at least exponentially fast error scaling

A mobile multi-sensor platform for building reconstruction integrating terrestrial and autonomous UAV-based close range data acquisition

Photogrammetric data capture of complex 3D objects using UAV imagery has become commonplace. Software tools based on algorithms like Structure-from-Motion and multi-view stereo image matching enable the fully automatic generation of densely meshed 3D point clouds. In contrast, the planning of a suitable image network usually requires considerable effort of a human expert, since this step directly influences the precision and completeness of the resulting point cloud. Planning of suitable camera stations can be rather complex, in particular for objects like buildings, bridges and monuments, which frequently feature strong depth variations to be acquired by high resolution images at a short distance. Within the paper, we present an automatic flight mission planning tool, which generates flight lines while aiming at camera configurations, which maintain a roughly constant object distance, provide sufficient image overlap and avoid unnecessary stations. Planning is based on a coarse Digital Surface Model and an approximate building outline. As a proof of concept, we use the tool within our research project MoVEQuaD, which aims at the reconstruction of building geometry at sub-centimetre accuracy

Postfeminist Media Cultures

This entry provides an overview of postfeminism, which has become central in the last two decades not only within feminist cultural discourse but also within neoliberal discourses and popular culture. The dominant attempts to conceptualize postfeminism often bring to the surface approaches that are complex and contradictory in nature. For instance, postfeminism is viewed as a theoretical framework, as a sensibility, as an expansion of feminist theory, or as a rejection of it. The discussion of postfeminism against the backdrop of media productions further highlights its implications for women and gender representation. A look at quintessential postfeminist texts shows, for instance, that postfeminism essentially problematizes contemporary constructions of gender as it simultaneously evokes and rejects basic feminist tenets

Chiral Symmetry and the Nucleon's Vector Strangeness Form Factors

The nucleon's strange-quark vector current form factors are studied from the perspective of chiral symmetry. It is argued that chiral perturbation theory cannot yield a prediction for the strangeness radius and magnetic moment. Arrival at definite predictions requires the introduction of additional, model-dependent assumptions which go beyond the framework of chiral perturbation theory. A variety of such model predictions is surveyed, and the credibility of each is evaluated. The most plausible prediction appears in a model where the unknown chiral counterterms are identified with $t$-channel vector meson exchange amplitudes. The corresponding prediction for the mean square Dirac strangeness radius is $\langle r_s^2\rangle = 0.24$ fm$^2$, which would be observable in up-coming semileptonic determinations of the nucleon's strangeness form factors.Comment: LaTex 31 pages, four figures available from authors

The influence of anesthetics, neurotransmitters and antibiotics on the relaxation processes in lipid membranes

In the proximity of melting transitions of artificial and biological membranes fluctuations in enthalpy, area, volume and concentration are enhanced. This results in domain formation, changes of the elastic constants, changes in permeability and slowing down of relaxation processes. In this study we used pressure perturbation calorimetry to investigate the relaxation time scale after a jump into the melting transition regime of artificial lipid membranes. This time corresponds to the characteristic rate of domain growth. The studies were performed on single-component large unilamellar and multilamellar vesicle systems with and without the addition of small molecules such as general anesthetics, neurotransmitters and antibiotics. These drugs interact with membranes and affect melting points and profiles. In all systems we found that heat capacity and relaxation times are related to each other in a simple manner. The maximum relaxation time depends on the cooperativity of the heat capacity profile and decreases with a broadening of the transition. For this reason the influence of a drug on the time scale of domain formation processes can be understood on the basis of their influence on the heat capacity profile. This allows estimations of the time scale of domain formation processes in biological membranes.Comment: 12 pages, 6 figure

Extracting Br(omega->pi^+ pi^-) from the Time-like Pion Form-factor

We extract the G-parity-violating branching ratio Br(omega->pi^+ pi^-) from the effective rho-omega mixing matrix element Pi_{rho omega}(s), determined from e^+e^- -> pi^+ pi^- data. The omega->pi^+ pi^- partial width can be determined either from the time-like pion form factor or through the constraint that the mixed physical propagator D_{rho omega}^{mu nu}(s) possesses no poles. The two procedures are inequivalent in practice, and we show why the first is preferred, to find finally Br(omega->pi^+ pi^-) = 1.9 +/- 0.3%.Comment: 12 pages (published version

Collision times in pi-pi and pi-K scattering and spectroscopy of meson resonances

Using the concept of collision time (time delay) introduced by Eisenbud and Wigner and its connection to on-shell intermediate unstable states, we study mesonic resonances in pi-pi and pi-K scattering. The time-delay method proves its usefulness by revealing the spectrum of the well-known rho- and K*-mesons and by supporting some speculations on rho-mesons in the 1200 MeV region. We use this method further to shed some light on more speculative meson resonances, among others the enigmatic scalars. We confirm the existence of chiralons below 1 GeV in the unflavoured and strange meson sector.Comment: 22 pages LaTex, 8 figure

Single electron response and energy resolution of a Micromegas detector

Micro-Pattern Gaseous Detectors (MPGDs) such as Micromegas or GEM are used in particle physics experiments for their capabilities in particle tracking at high rates. Their excellent position resolutions are well known but their energy characteristics have been less studied. The energy resolution is mainly affected by the ionisation processes and detector gain fluctuations. This paper presents a method to separetely measure those two contributions to the energy resolution of a Micromegas detector. The method relies on the injection of a controlled number of electrons. The Micromegas has a 1.6-mm drift zone and a 160-$\mu$m amplification gap. It is operated in Ne 95%-iC$\mathrm{_4}$H$\mathrm{_{10}}$ 5% at atmospheric pressure. The electrons are generated by non-linear photoelectric emission issued from the photons of a pulsed 337-nm wavelength laser coupled to a focusing system. The single electron response has been measured at different gains (3.7 10$\mathrm{^4}$, 5.0 10$\mathrm{^4}$ and 7.0 10$\mathrm{^4}$) and is fitted with a good agreement by a Polya distribution. From those fits, a relative gain variance of 0.31$\pm$0.02 is deduced. The setup has also been characterised at several voltages by fitting the energy resolution measured as a function of the number of primary electrons, ranging from 5 up to 210. A maximum value of the Fano factor (0.37) has been estimated for a 5.9 keV X-rays interacting in the Ne 95%-iC$\mathrm{_4}$H$\mathrm{_{10}}$ 5% gas mixture.Comment: Preprint submitted to Nuclear Instrumentation and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment; Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment in press (2009