Phase diagram and dynamic response functions of the Holstein-Hubbard model

We present the phase diagram and dynamical correlation functions for the Holstein-Hubbard model at half filling and at zero temperature. The calculations are based on the Dynamical Mean Field Theory. The effective impurity model is solved using Exact Diagonalization and the Numerical Renormalization Group. Excluding long-range order, we find three different paramagnetic phases, metallic, bipolaronic and Mott insulating, depending on the Hubbard interaction U and the electron-phonon coupling g. We present the behaviour of the one-electron spectral functions and phonon spectra close to the metal insulator transitions.Comment: contribution to the SCES04 conferenc

Knowledge-based intelligent error feedback in a Spanish ICALL system

This paper describes the Spanish ICALL system ESPADA which helps language learners to improve their syntactical knowledge. The most important parts of ESPADA for the learner are a Demonstration Module and an Analysis Module. The Demonstration Module provides animated presentation of selected grammatical information. The Analysis Module is able to parse ill-formed sentences and to give adequate feedback on 28 different error types from different levels of language use (syntax, semantics, agreement). It contains a robust chart-based island parser which uses a combination of mal-rules and constraint relaxation to ensure that learner input can be analysed and appropriate error feedback can be generated

Onset of metallic ferromagnetism in a doped spin-orbital chain

Starting from a spin-orbital model for doped manganites, we investigate a competition between ferromagnetic and antiferromagnetic order in a one-dimensional model at finite temperature. The magnetic and orbital order at half filling support each other and depend on a small antiferromagnetic superexchange between t_{2g} spins and on an alternating Jahn-Teller potential. The crossover to a metallic ferromagnetic phase found at finite doping is partly suppressed by the Jahn-Teller potential which may localize e_g electrons.Comment: 6 pages, 4 figures, contribution to ICTP Ustron, 2004, see phys. stat. sol. at http://www.interscience.wiley.co

Manure for Vegetables: Farm practice recommendations for minimizing human pathogenic bacteria contamination in vegetable production

To obtain sufficient yields in vegetable production, fertilization with nitrogen, phosphorus and potassium is necessary. Manure is a valuable source of these nutrients. This guide is an overview of the latest scientific information concerning potential food safety risks related to the application of manure in vegetable production, and gives recommendations for minimizing these risks. While the focus is on manure handling, other potential contamination sources are also briefly addressed

On the Legitimacy of Political Communities

The paper consists of two parts. The first part deals with the normative legitimacy of political communities, such as states and confederations, in general, i.e. their acceptability in light of reasonable standards of efficiency, common good, and justice from the viewpoints of their members on the one hand (internal legitimacy) and their social surroundings on the other (external legitimacy). The requirements of both aspects of legitimacy are specified in a twofold way: as normative ideals and as minimum standards. As to the latter, a political community's legitimacy minimally requires that it effectively guarantees the fundamental human rights of its members and complies with certain basic precepts of a peaceful and generally beneficial international order. On this basis, the second part scrutinizes the legitimacy of the European Union with regard to its internal and external aspects. This attempt leads to a mixed result. Even though the EU can certainly be regarded, by and large, as a desirable project, it also suffers from a number of considerable defects that weaken its legitimacy.normative legitimacy, political communities, efficiency, common good, justice, internal legitimacy, external legitimacy, European Union