Reduction of Vector and Axial--Vector Fields in a Bosonized Nambu--Jona--Lasinio Model

We derive the effective action for pseudoscalar mesons by integrating out vector and axial--vector collective fields in the generating functional of the bosonized NJL--model. The corresponding modifications of the nonlinear effective Lagrangian and the bosonized currents, arising at $O(p^4)$, are discussed.Comment: 30p. 1 fig. on reques

Radiative Kaon Decays and CPCP Violation

The amplitudes of $K \rightarrow \pi \gamma^* \rightarrow \pi e^+e^-$ and $K \rightarrow \pi \pi \gamma$ decays have been calculated within chiral Lagrangian approach including higher-order derivative terms and meson loops. The selfconsistency of the simultaneous description of the experimental data on the nonleptonic and radiative kaon decays have been demonstrated. We estimate the effects of ``indirect'' and ``direct'' $CP$-violation in $K^0_L \rightarrow \pi^0 e^+e^-$ decays and discuss $CP$-violating charge asymmetries in $K^{\pm} \rightarrow \pi^{\pm} \pi^0 \gamma$ decays.Comment: 25 p., DESY 93-06

Media And Information Technologies In Teacher Education - Plea For A Minimum Curriculum

In diesem Beitrag werden konzeptionelle Überlegungen für die Integration eines Lehrkomplexes «Neue Medien und Informationstechnologien» im Rahmen des erziehungswissenschaftlichen Grundstudiums in der ersten Phase der Lehramtsausbildung vorgestellt. Dabei stützen sich die Autoren vor allem auf die Erfahrungen und Ergebnisse des zweijährigen Modellversuchs «Informatische Bildung für Lehrerstudenten», der im Rahmen des erziehungswissenschaftlichen Teils der Lehramtsausbildung an der Humboldt Universität zu Berlin sehr erfolgreich und mit hoher Akzeptanz auf Seiten der Studenten durchgeführt wurde.This article presents conceptual considerations for the integration of a teaching complex "New Media and Information Technologies" within the framework of the basic studies in educational science in the first phase of teacher training. In doing so, the authors draw primarily on the experiences and results of the two-year pilot project "Informatics Education for Teacher Trainees", which was carried out very successfully and with a high level of acceptance on the part of the students within the framework of the educational science part of teacher training at the Humboldt University in Berlin

On the p4p^4--corrections to K→3πK \to 3\pi decay amplitudes in nonlinear and linear chiral models

The calculations of isotopic amplitudes and their results for the direct $CP$--violating charge asymmetry in $K^\pm \to 3\pi$ decays within the nonlinear and linear ($\sigma$--model) chiral Lagrangian approach are compared with each other. It is shown, that the latter, taking into account intermediate scalar resonances, does not reproduce the $p^4$--corrections of the nonlinear approach introduced by Gasser and Leutwyler, being saturated mainly by vector resonance exchange. The resulting differences concerning the $CP$ violation effect are traced in some detail.Comment: 14 page

Heat-Kernel Calculation of Quark Determinant and Computer Algebra

In this paper there we describe the calculational background of deriving a strong meson Lagrangian from the Nambu--Jona-Lasinio quark model using the computer algebra systems FORM and REDUCE in recursive algorithms, based on the heat-kernel method for the calculation of the quark determinant.Comment: LATEX, 11 p., DESY 92-15

An ensemble neural network atmospheric correction for Sentinel-3 OLCI over coastal waters providing inherent model uncertainty estimation and sensor noise propagation

Accurate atmospheric correction (AC) is a prerequisite for quantitative ocean colour remote sensing and remains a challenge in particular over coastal waters. Commonly AC algorithms are validated by establishing a mean retrieval error from match-up analysis, which compares the satellite-derived surface reflectance with concurrent ground radiometric observations. Pixel-based reflectance uncertainties however, are rarely provided by AC algorithms and those for the operational Ocean and Land Colour Instrument (OLCI) marine reflectance product are not yet recommended for use. AC retrieval errors and uncertainties directly determine the quality with which ocean colour products can be estimated from the marine surface reflectance. Increasingly there is also the need for reflectance uncertainty products to be used as data assimilation inputs into biogeochemical models. This paper describes the development of a new coastal AC algorithm for Sentinel-3 OLCI that provides pixel-based estimation of the inherent model inversion uncertainty and sensor noise propagation. The algorithm is a full-spectral model-based inversion of radiative transfer (RT) simulations in a coupled atmosphere–ocean system using an ensemble of artificial neural networks (ANN) that were initialized differently during the training process, but composed of the same network architecture. The algorithm has been validated against in-situ radiometric observations across a wide range of optical water types, and has been compared with the latest EUMETSAT operational Level 2 processor IPF-OL-2 v7.01. In this analysis we found that the ensemble ANN showed improved performance over the operational Level 2 processor with a band-averaged (412–708 nm) mean absolute percentage error (MAPE) of 16% compared to 37% and a four-times lower band-averaged bias of -0.00045 sr-1. In the ensemble inversion process we account for three uncertainty components: (1) the total model variance that describes the variance of the data from the different ANNs, (2) the prediction variance of the mean, which is based on calculations of the RT simulations and (3) the instrument noise variance of the mean by propagating the OLCI spectral signal-to-noise ratios (SNR). To study algorithm performance and to quantify the contribution of the different uncertainty components to the total uncertainty, we applied the algorithm to an optically complex full resolution (FR) test scene covering coastal waters of the Great Barrier Reef, Australia. The uncertainties associated with the instrument noise variance were found to be two orders of magnitude lower than the uncertainty components of the prediction and total model variances. The overall largest uncertainty component in our uncertainty framework is attributed to the total model inversion error from averaging the responses of the slightly different adapted networks in the ensemble. The algorithm is made publicly available as a Python/C plugin for the Sentinel Application Platform (SNAP)

Calculation of Heat-Kernel Coefficients and Usage of Computer Algebra

The calculation of heat-kernel coefficients with the classical DeWitt algorithm has been discussed. We present the explicit form of the coefficients up to $h_5$ in the general case and up to $h_7^{min}$ for the minimal parts. The results are compared with the expressions in other papers. A method to optimize the usage of memory for working with large expressions on universal computer algebra systems has been proposed.Comment: 12 pages, LaTeX, no figures. Extended version of contribution to AIHENP'95, Pisa, April 3-8, 199