Renormalization of a gapless Hartree-Fock approximation to a theory with spontaneously broken O(N)-symmetry

The renormalization of a gapless Phi-derivable Hartree--Fock approximation to the O(N)-symmetric lambda*phi^4 theory is considered in the spontaneously broken phase. This kind of approach was proposed by three of us in a previous paper in order to preserve all the desirable features of Phi-derivable Dyson-Schwinger resummation schemes (i.e., validity of conservation laws and thermodynamic consistency) while simultaneously restoring the Nambu--Goldstone theorem in the broken phase. It is shown that unlike for the conventional Hartree--Fock approximation this approach allows for a scale-independent renormalization in the vacuum. However, the scale dependence still persists at finite temperatures. Various branches of the solution are studied. The occurrence of a limiting temperature inherent in the renormalized Hartree--Fock approximation at fixed renormalization scale mu is discussed.Comment: 11 pages, 14 figures / Version accepted by Phys. Rev. D: title and one reference change

The German Vision of Industry 4.0 Applied in Organic Farming

The first industrial revolution was the invention of the steam engine. With the advent of conveyor belts and electricity, the second industrial revolution arose. After the third revolution, the automation, the fourth industrial revolution takes place with the complete networking of all machines, workers, consumers, and products. In Germany, this is called Industry 4.0. Increasing digitization makes it possible to collect, store, analyze, and communicate large amounts of data. By digitizing farms, a network of different sensors can analyze the nutrient content and the soil texture in real time. This information can be evaluated and the plant distribution can be managed across all networked farms. This leads to the right field being used for the right plant at the right time. Real-time data processing makes it possible to monitor and control the nutrient intake over the entire growth period. This allows the field to specifically ask for water or the right fertilizer for its plants. This saves resources and protects the environment. All the prepared information can give the farmer an exact status about his products and fields via an interface. This horizontal networking within the farm and the vertical networking across different farms can lead to increased efficiency and cheaper products. The use of robots can create a fully automatic farm. For this undertaking, it is necessary to process the complex information of a farm with a self-learning system. At the Westcoast University of Applied Science, for example, a robot is being researched to automatically remove the weeds. The prototype of the robot that moves fully autonomously across the field classifies the plants and destroys the weeds

Gapless Hartree-Fock Resummation Scheme for the O(N) Model

A modified selfconsistent Hartree-Fock approximation to the lambda*phi^4 theory with spontaneously broken O(N) symmetry is proposed. It preserves all the desirable features, like conservation laws and thermodynamic consistency, of the selfconsistent Dyson scheme generated from a 2PI functional, also known as the Phi-derivable scheme, while simultaneously respecting the Nambu-Goldstone theorem in the chiral-symmetry broken phase. Various approximate resummation schemes are discussed.Comment: 13 pages, 10 figures / Version accepted by Phys. Rev. D: the introduction has been expanded by a few remarks in order to further clarify the goal of the pape

Renormalization in Self-Consistent Approximations schemes at Finite Temperature I: Theory

Within finite temperature field theory, we show that truncated non-perturbative self-consistent Dyson resummation schemes can be renormalized with local counter-terms defined at the vacuum level. The requirements are that the underlying theory is renormalizable and that the self-consistent scheme follows Baym''s $\Phi$-derivable concept. The scheme generates both, the renormalized self-consistent equations of motion and the closed equations for the infinite set of counter terms. At the same time the corresponding 2PI-generating functional and the thermodynamical potential can be renormalized, in consistency with the equations of motion. This guarantees the standard $\Phi$-derivable properties like thermodynamic consistency and exact conservation laws also for the renormalized approximation schemes to hold. The proof uses the techniques of BPHZ-renormalization to cope with the explicit and the hidden overlapping vacuum divergences.Comment: 22 Pages 1 figure, uses RevTeX4. The Revision concerns the correction of some minor typos, a clarification concerning the real-time contour structure of renormalization parts and some comments concerning symmetries in the conclusions and outloo

Three-dimensional track reconstruction for directional Dark Matter detection

Directional detection of Dark Matter is a promising search strategy. However, to perform such detection, a given set of parameters has to be retrieved from the recoiling tracks : direction, sense and position in the detector volume. In order to optimize the track reconstruction and to fully exploit the data of forthcoming directional detectors, we present a likelihood method dedicated to 3D track reconstruction. This new analysis method is applied to the MIMAC detector. It requires a full simulation of track measurements in order to compare real tracks to simulated ones. We conclude that a good spatial resolution can be achieved, i.e. sub-mm in the anode plane and cm along the drift axis. This opens the possibility to perform a fiducialization of directional detectors. The angular resolution is shown to range between 20$^\circ$ to 80$^\circ$, depending on the recoil energy, which is however enough to achieve a high significance discovery of Dark Matter. On the contrary, we show that sense recognition capability of directional detectors depends strongly on the recoil energy and the drift distance, with small efficiency values (50%-70%). We suggest not to consider this information either for exclusion or discovery of Dark Matter for recoils below 100 keV and then to focus on axial directional data.Comment: 27 pages, 20 figure

Low energy \omega (\to \pi^0 \gamma) meson photoproduction in the nucleus

The $\pi^0 \gamma$ invariant mass distribution spectra in the $(\gamma, \pi^0\gamma)$ reaction were measured by TAPS/ELSA collaboration to look for the hadron parameters of the $\omega$ meson in Nb nucleus. We study the mechanism for this reaction, where we consider that the elementary reaction in Nb nucleus proceeds as $\gamma N \to \omega N; ~ \omega \to \pi^0\gamma$. The $\omega$ meson photoproduction amplitude for this reaction is extracted from the measured four momentum transfer distribution in the $\gamma p \to \omega p$ reaction. The propagation of the $\omega$ meson and the distorted wave function for the $\pi^0$ meson in the final state are described by the eikonal form. The $\omega$ and $\pi^0$ mesons nucleus optical potentials, appearing in the $\omega$ meson propagator and $\pi^0$ meson distorted wave function respectively, are estimated using the "$t\varrho$" approximation. The effects of pair correlation and color transparency are also studied. The calculated results do not show medium modification for the $\omega$ meson produced in the nucleus for its momentum greater than 200 MeV. It occurs since the $\omega$ meson dominantly decays outside the nucleus. The dependence of the cross section on the final state interaction is also investigated. The broadening of the $\omega$ meson mass distribution spectra is shown to occur due to the large resolution width associated with the detector used in the experiment.Comment: 14 pages, 6 figure

Renormalization in Self-Consistent Approximation schemes at Finite Temperature III: Global Symmetries

We investigate the symmetry properties for Baym's $\Phi$-derivable schemes. We show that in general the solutions of the dynamical equations of motion, derived from approximations of the $\Phi$-functional, do not fulfill the Ward-Takahashi identities of the symmetry of the underlying classical action, although the conservation laws for the expectation values of the corresponding Noether currents are fulfilled exactly for the approximation. Further we prove that one can define an effective action functional in terms of the self-consistent propagators which is invariant under the operation of the same symmetry group representation as the classical action. The requirements for this theorem to hold true are the same as for perturbative approximations: The symmetry has to be realized linearly on the fields and it must be free of anomalies, i.e., there should exist a symmetry conserving regularization scheme. In addition, if the theory is renormalizable in Dyson's narrow sense, it can be renormalized with counter terms which do not violate the symmetry.Comment: 32 papges, 3 figures, uses ReVTeX 4, V2: Added one more reference, V3: Corrected some typos, added two more sections about the large-N expansio

Coulomb Distortion Effects for (e,e'p) Reactions at High Electron Energy

We report a significant improvement of an approximate method of including electron Coulomb distortion in electron induced reactions at momentum transfers greater than the inverse of the size of the target nucleus. In particular, we have found a new parametrization for the elastic electron scattering phase shifts that works well at all electron energies greater than 300 $MeV$. As an illustration, we apply the improved approximation to the $(e,e'p)$ reaction from medium and heavy nuclei. We use a relativistic ``single particle'' model for $(e,e'p)$ as as applied to $^{208}Pb(e,e'p)$ and to recently measured data at CEBAF on $^{16}O(e,e'p)$ to investigate Coulomb distortion effects while examining the physics of the reaction.Comment: 14 pages, 3 figures, PRC submitte

Human error analysis: Review of past accidents and implications for improving robustness of system design

Since the establishment of the high-technology industry and industrial systems, developments of new materials and fabrication techniques, associated with cutting-edge structural and engineering assessments, are contributing to more reliable and consistent systems, thus reducing the likelihood of losses. However, recent accidents are acknowledged to be linked to human factors which led to catastrophic consequences. Therefore, the understanding of human behavioural characteristics interlaced with the actual technology aspects and organisational context is of paramount importance for the safety & reliability field. This study first approaches this multidisciplinary problem by classifying and reviewing 200 major accident data from insurance companies and regulatory authorities under the Cognitive Reliability and Error Analysis framework. Then, specific attention is dedicated to discuss the implications for improving robustness of system design and tackling the surrounding factors and tendencies that could lead to the manifestation of human errors

Spatiotemporal profile of peri-saccadic contrast sensitivity

Sensitivity to luminance contrast is reduced just before and during saccades (saccadic suppression), whereas sensitivity to color contrast is unimpaired peri-saccadically and enhanced post-saccadically. The exact spatiotemporal map of these perceptual effects is as yet unknown. Here, we measured detection thresholds for briefly flashed Gaussian blobs modulated in either luminance or chromatic contrast, displayed at a range of eccentricities. Sensitivity to luminance contrast was reduced peri-saccadically by a scaling factor, which was almost constant across retinal space. Saccadic suppression followed a similar time course across all tested eccentricities and was maximal shortly after the saccade onset. Sensitivity to chromatic contrast was enhanced post-saccadically at all tested locations. The enhancement was not specifically linked to the execution of saccades, as it was also observed following a displacement of retinal images comparable to that caused by a saccade. We conclude that luminance and chromatic contrast sensitivities are subject to distinct modulations at the time of saccades, resulting from independent neural processes