Finite-temperature evaluation of the Fermi density operator

A rational expansion of the Fermi density operator is proposed. This approach allows to calculate efficiently physical properties of fermionic systems at finite temperatures without solving an eigenvalue problem. Using N evaluations of the Green's function, the Fermi density operator can be approximated, subject to a given precision, in the energy interval from -A to infinity with A proportional to N. The presented method may become especially useful for electronic structure calculations involving the calculation of charge densities.Comment: 6 pages, 4 Postscript figures, submitted to J. Comp. Phy

Farewell, welfare state – hello, welfare regions? Chances and constraints of welfare management in the German federal system

The German welfare state is in crisis. Alarming long-term demographic trends, the still not fully digested consequences of German unification and the current economic downturn in much of the Eurozone have combined to create an urgent need for welfare reform. Yet the constitutional arrangements which govern the German political system, and well-entrenched political practice, mean that any such reform process is a daunting challenge. Thus, the welfare crisis is also a crisis of German-style co-operative federalism. Current empirical evidence makes for uncomfortable reading, and triggers debate on the nature of the German federation: have the two constitutional principles of federalism and establishing equal living conditions throughout the federation become mutually exclusive? However, as much of the welfare state is centred on the best utilisation of scarce financial resources, it is debatable to what extent alterations in the functional distribution of welfare responsibilities among the territorial levels of government can be regarded as a solution for the current problems. The article concludes that in the search for long-term sustainability of the welfare state the territorial dimension is likely to remain a secondary issue