Interorbital charge transfers and Fermi-surface deformations in strongly correlated metals: models, BaVS3_3 and Nax_{x}CoO2_2

Fermi-surface deformations in strongly correlated metals, in comparison to results from band-structure calculations, are investigated. We show that correlation-induced interband charge transfers in multi-orbital systems may give rise to substantial modifications of the actual Fermi surface. Depending in particular on the relative strength of the crystal-field splitting and of the Hund's exchange coupling, correlations may either reinforce orbital polarization or tend to compensate differences in orbital occupancies, as demonstrated by investigating a 2-band Hubbard model in the framework of dynamical mean field theory (DMFT). The physical implications of such interorbital charge transfers are then explored in two case studies: BaVS$_3$ and Na$_x$CoO$_2$. By means of the DMFT in combination with the local density approximation (LDA) to density functional theory (DFT), new insights in the underlying mechanism of the metal-to-insulator transition (MIT) of BaVS$_3$ are obtained. A strong charge redistribution in comparison to LDA calculations, i.e., a depletion of the broader $A_{1g}$ band in favor of the narrower $E_g$ bands just above the MIT is found. In addition, the intriguing problem of determining the Fermi surface in the strongly correlated cobaltate system Na$_{x}$CoO$_2$ is discussed.Comment: final versio

Needed now: a world environment and development organization

Global environmental policy certainly could gain strength if the management of the United Nations Environment Programme (UNEP) or of the UN Commission on Sustainable Development (CSD) were made more efficient. However, such a minimalist strategy of efficiency improvement is no panacea: it can only be an element, not the core of a new global environmental policy. Therefore, instead of merely calling for improved efficiency and coordination, in this paper a proposal is made to establish a World Environment and Development Organization (WEDO) as a new specialized agency of the United Nations. At the very least, such an Organization should integrate UNEP, the CSD and the relevant Convention Secretariats (climate, biodiversity, desertification conventions); close cooperation with the Bretton Woods institutions - the World Bank, the International Monetary Fund (IMF), the World Trade Organization (WTO) - and the existing UN specialized agencies would need to be ensured. Also, ideas are being presented on the decision-making procedures, the participation of Non-Governmental Organizations (NGOs), and on the financing of such a World Environment and Development Organization. --

Importance of interorbital charge transfers for the metal-to-insulator transition of BaVS3_3

The underlying mechanism of the metal-to-insulator transition (MIT) in BaVS$_3$ is investigated, using dynamical mean-field theory in combination with density functional theory. It is shown that correlation effects are responsible for a strong charge redistribution, which lowers the occupancy of the broader \a1g band in favor of the narrower $E_g$ bands. This resolves several discrepancies between band theory and the experimental findings, such as the observed value of the charge-density wave ordering vector associated with the MIT, and the presence of local moments in the metallic phase.Comment: improved discussion, new figure, added reference

Stand und Fortentwicklung der internationalen Klimapolitik

„... an den Küsten – liest man – steigt die Flut / Der Sturm ist da, die wilden Meere hupfen / An Land, um dicke Dämme zu zerdrücken“ – dieses „Weltende“, das Jakob von Hoddis 1911, in der Endzeitstimmung vor Beginn des ersten Weltkrieges, erfühlte, findet knapp neunzig Jahre später eine ganz neue, nicht weniger dramatische Interpretation. „Es ist vermutlich zu spät, um die globale Erwärmung zu verhindern“, so vermeldete das Umweltprogramm der Vereinten Nationen im Herbst 1999. So einfach, so knapp lässt sich die kommende Katastrophe des 21. Jahrhunderts umreißen. Wenn die derzeitigen Prognosen eintreffen, wird der Meeresspiegel steigen, werden Klimazonen sich verschieben, wird die Menschheit der Gefahr unvorhersehbarer Risiken eines veränderten und kaum verstandenen Klimasystems ausgesetzt sein (allgemein hierzu Schellnhuber 1998). --

Competing itinerant and localized states in strongly correlated BaVS3_3

The electronic structure of the quasi-lowdimensional vanadium sulfide \bavs3 is investigated for the different phases above the magnetic ordering temperature. By means of density functional theory and its combination with dynamical-mean field theory, we follow the evolution of the relevant low-energy electronic states on cooling. Hence we go in the metallic regime from the room temperature hexagonal phase to the orthorhombic phase after the first structural transition, and close with the monoclinic insulating phase below the metal-insulator transition. Due to the low symmetry and expected intersite correlations, the latter phase is treated within cellular dynamical mean-field theory. It is generally discussed how the intriguing interplay between band-structure and strong-correlation effects leads to the stabilization of the various electronic phases with decreasing temperature.Comment: 12 pages, submitted to PR

Die POP-Konvention: Das neue Chemikalien-Regime der Vereinten Nationen

Die Freisetzung persistenter organischer Schadstoffe (POPs) gilt inzwischen als ernstes globales Umweltproblem. Ende Juni 1998 trat im kanadischen Montreal ein zwischenstaatlicher Verhandlungsausschuß zusammen, um einen weltweiten Vertrag »über die Umsetzung internationaler Maßnahmen betreffend gewisser persistenter organischer Schadstoffe« auszuarbeiten. Nach der Klimakonvention, der Biodiversitätskonvention und der Desertifikationskonvention wird die UNChemikalienkonvention die vierte zentrale »Rio-Konvention« sein, in Nachfolge zum Erdgipfel von Rio de Janeiro von 1992. In diesem Papier werden diese Verhandlungen seit ihrer Entstehung und in ihren seitherigen Ergebnissen analysiert. Wir umreißen das Problem und die Datenlage zur Interessenstruktur, verknüpfen die derzeitigen mit den älteren Verhandlungen, analysieren den Stand der Politik in wesentlichen Konfliktfeldern, auch mit Blick auf andere Regime, um dann im Abschlußkapitel einige Perspektiven für die weiteren Verhandlungen und mögliche intensivere Forschungsarbeiten über die POP-Diplomatie zu skizzieren. Unsere empirische Basis ist die Auswertung der offiziellen Verhandlungsdokumente, eine Reihe von Interviews mit Verhandlungsteilnehmerinnen und -teilnehmen! sowie die verfügbare Sekundärliteratur. -- Persistent organic pollutants (POP) have been identified as major global environmental threat. In June 1998, delegates of several governments convened in Montreal, Canada, to start negotiating a UN convention »for implementing international action on certain persistent organic pollutants«. This treaty will be the fourth major Rio Convention, after the 1992 Climate Convention, the 1992 Convention on Biological Diversity and the 1994 Desertification Convention. This paper analyses the POP negotiations with a view both to their history and their (still preliminary) results. We sketch the problem and available data on state interests; link present negotiations to other issue areas of international environmental diplomacy; examine the emerging regime in major areas of conflict; and offer some perspectives on the next round of negotiations and possible future research projects on »POP diplomacy«. Our empirical basis are official documents from the negotiations, a series of interviews with delegates as well as some secondary sources.

Institutional reform of international environmental policy: advancing the debate on a world environment organization

"With the onset of the new millennium, the longstanding need for reform of the United Nations system has gained new momentum. Efficiency gains and better coordination are desirable, though not sufficient to bring about improvement in international relations. It could therefore make sense to look for institutional innovations that would upgrade the pressing tasks of environmental and development policy in the eyes of national governments, international organizations, and nongovernmental organizations, improve the institutional setting for the negotiation and implementation of new agreements and action programs, and strengthen the action capacity of the developing countries on these matters. The present paper points to and elaborates the need for a 'World Environment and Development Organization' within the United Nations system, and outlines the shape it might be given. The intention here is to carry the debate, which has made considerable headway, into the science of politics and development. How will the expert community in the field of foreign relations and development cooperation, based on their theories and empirical knowledge, respond to the proposal?" (author's abstract)"Mit dem Beginn des neuen Jahrhunderts hat die lang anstehende Reform des Systems der Vereinten Nationen neue Dringlichkeit erhalten. Effizienzgewinne und bessere Koordination sind wünschenswert, aber nicht hinreichend, insbesondere, wenn es um die Stärkung der Umweltkompetenz geht. In diesem Beitrag wird die Notwendigkeit der Etablierung einer Sonderorganisation für Umwelt und Entwicklung im System der Vereinten Nationen begründet und in ihren Umrissen vorgestellt. Der Vorschlag zielt insbesondere darauf, die Diskussion über notwendige institutionelle Innovationen auf der globalen Ebene zu stimulieren. Wie werden Experten für internationale Beziehungen und Entwicklungszusammenenarbeit auf diese Empfehlung reagieren?" (Autorenreferat

National Climate Change Policy: Are the New German Energy Policy Initiatives in Conflict with WTO Law?

This paper addresses German energy policy instruments and their compatibility with WTO rules. Germany and the EU are forerunners in international climate change policy and driving forces behind the 1997 Kyoto Protocol. German energy policy includes approaches to foster electricity generation from renewable resources. Our major question is whether both the policy tools currently applied (standards, taxes and subsidies) and those under consideration (labels, green certificates and border tax adjustment) are compatible with WTO rules. Our findings are that currently neither the design nor the application of the policy instruments are in conflict with WTO rules. However, the setting of production standards for electricity supply is the crucial issue in this debate and if trade in electricity increases, so will the potential for conflict. Rejecting imports because of the way electricity was produced could lead to disputes and to a need for settlements by the WTO legal system. Moreover, when introducing tools like green certificates or border tax adjustments, it is important to find the balance between effectively fostering the reduction of global emissions and eligibility under WTO law.Energy policy; World Trade Organization; global environmental policy; processes and production methods; labels; green certificates; taxes; border tax adjustment; subsidies.

Institutionelles Lernen in der Weltumweltpolitik

Auf dem >Erdgipfel

Social-Ecological Peace – A framework to analyze the transition from violence to peace in post-conflict areas, applied to Aceh, Indonesia

While the analysis of peace often stops with "negative peace" in conflict studies (Shields 2017), critical structural analyses of a transition towards peace risk to analytically emphasize how wartime structures extend into post-conflict times (see e.g. Lee 2020). In this article, by engaging with the two fields of conflict studies and political ecology, a framework is developed that allows a critical analysis of resilient structures and discourses from times of conflict, as well as of possible leverage points that could support a transition towards what is here conceptualized as "social ecological peace". The framework hence helps to understand in how far dimensions of prior violence have transformed into peace, and if certain dimensions of violence have continued, even though they manifest themselves in a different way. The framework builds on Galtung’s conceptualization of violence and peace, but realigns "cultural violence" with Pierre Bourdieu's "symbolic violence". Additionally, for extending the framework with an ecological dimension and historical dimension, the notion of 'slow violence' by Rob Nixon is introduced. Applying the framework to Aceh, Indonesia, shows how cultural peace allows individuals to narrate and act out of a new identity, and in this way, enables them to put into effect structures of a new era of positive social-ecological peace. At the same time, discourses that are inherited from wartime and transform into peace time structures risk to carry violence in them. It becomes important to lay open the structural effects of the very discourses that have supported Aceh’s autonomy, so that they may not further extend structural violence into peace times. This is likely to remain a challenge in a context that is described as still negotiating and struggling to enhance its autonomy (Setyowati 2020a).publishedVersio