Nuclear quantum transport for barrier problems

A method is presented which allows one to introduce collective coordinates self-consistently, in distinction to the Caldeira-Leggett model. It is demonstrated how the partition function Z for the total nuclear system can be calculated to deduce information both on its level density as well as on the decay rate of unstable modes. For the evaluation of Z different approximations are discussed. A recently developed variational approach turns out superior to the conventional methods that include quantum effects on the level of local RPA. Dissipation is taken into account by applying energy smearing, simulating in this way the coupling to more complicated states. In principle, such a coupling must depend on temperature. Previous calculations along another microscopic approach show this fact to imply an intriguing variation of the transport coefficients of collective motion with T. The relevance of this feature is demonstrated for the thermal fission rate and for the formation probability of super-heavy elements.Comment: 8 pages, 4 figures, presented at FUSION03, Matsushima, Miyagi, Japan, Nov 12-15, 2003, to appear in Progress of Theoretical Physic

A note on the time evolution of the fission decay width under the influence of dissipation

The claim put forward in a recent paper by B. Jurado, K.-H. Schmidt and J. Benlliure that the transient effect of nuclear fission may be described simply as a relaxation process in the upright oscillator around the potential minimum is refuted. Some critical remarks on the relevance of this effect in general are added.Comment: 6 pages, LaTex, no figures; final, shorter version, to appear in PL

Influence of microscopic transport coefficients on the formation probabilities for super-heavy elements

The formation probability is shown to increase by a few orders of magnitude if microscopic transport coefficients are used rather than those of the common macroscopic pictures. Quantum effects in collective dynamics are taken into account through the fluctuating force, as exhibited in diffusion coefficients for a Gaussian process. In the range of temperatures considered here, they turn out to be of lesser importance.Comment: 20 pages, 9 figures, replaced by revised version accepted for publication in NP

Demographic Change and Public Sector Budgets in a Federal System

This paper examines the effects of demographic change on public finances in a federal system. We develop a simple methodical procedure to measure the effect of demographic changes on public revenues and expenditures. We apply our method to the local, state and federal government sector as well as on the social security system in Germany. Our results suggest that demographic change will lead to significant vertical fiscal imbalances between the different layers of government. In addition we show, that subnational governments can generate a demographic dividend whereas the social security system and the federal government have to carry an additional burden due to ageing.fiscal federalism, demographic change, sustainability of public finances

Fission Decay Rates Determined from a Quantal Transport Equation

The decay of a metastable system is described by extending Kramers' method to the quantal regime. For temperatures above twice the crossover value we recover the result known from applying Euclidean path integrals to solvable models. Our derivation is not restricted to a linearly coupled heat bath of oscillators, and thus applicable to nuclear systems.Comment: 10 pages, Plain Tex, TU-Muenchen preprin

Demographiesensitivität und Nachhaltigkeit der Länder- und Kommunalfinanzen: Ein Ost-West-Vergleich

Der Beitrag untersucht die Auswirkungen des demographischen Wandels in Deutschland auf die öffentlichen Finanzen anhand des Konzeptes der Altersstrukturprofile. Der Fokus liegt dabei auf der Länder- und Gemeindeebene. Neben einer starken Demographiesensitivität der Ausgaben und Einnahmen zeigt sich, dass bis 2030 demographische Dividenden auf der Länder- und Gemeindeebene generiert werden können. Ostdeutschland profitiert von den demographischen Veränderungen stärker als Westdeutschland. Zusätzlich wird eine Analyse der Nachhaltigkeit der Länder- und Gemeindehaushalte präsentiert. Unsere Modellrechnungen zeigen, dass das Nahziel ausgeglichener Haushalte relativ unproblematisch auf der Länder- und Gemeindeebene erreicht werden kann. --Fiskalföderalismus,Öffentliche Finanzen,Demographischer Wandel,Nachhaltigkeit

On the nature of nuclear dissipation, as a hallmark for collective dynamics at finite excitation

We study slow collective motion of isoscalar type at finite excitation. The collective variable is parameterized as a shape degree of freedom and the mean field is approximated by a deformed shell model potential. We concentrate on situations of slow motion, as guaranteed, for instance, by the presence of a strong friction force, which allows us to apply linear response theory. The prediction for nuclear dissipation of some models of internal motion are contrasted. They encompass such opposing cases as that of pure independent particle motion and the one of "collisional dominance". For the former the wall formula appears as the macroscopic limit, which is here simulated through Strutinsky smoothing procedures. It is argued that this limit hardly applies to the actual nuclear situation. The reason is found in large collisional damping present for nucleonic dynamics at finite temperature $T$. The level structure of the mean field as well as the $T$-dependence of collisional damping determine the $T$-dependence of friction. Two contributions are isolated, one coming from real transitions, the other being associated to what for infinite matter is called the "heat pole". The importance of the latter depends strongly on the level spectrum of internal motion, and thus is very different for "adiabatic" and "diabatic" situations, both belonging to different degrees of "ergodicity".Comment: 50 pages plus 10 figures, uuencoded postscript file

Mean first passage time for nuclear fission and the emission of light particles

The concept of a mean first passage time is used to study the time lapse over which a fissioning system may emit light particles. The influence of the "transient" and "saddle to scission times" on this emission are critically examined. It is argued that within the limits of Kramers' picture of fission no enhancement over that given by his rate formula need to be considered.Comment: 4 pages, RevTex, 4 postscript figures; with correction of misprints; appeared in Phys. Rev. Lett.90.13270