Der Einfluß eines Sterndichtegradienten auf die Verteilung des Gravitations-Mikrofeldes in Sternhaufen

The probability distribution of the gravitational microfield at a fixed space point in a stellar cluster is determined using the Markov-method and neglecting statistical correlations between individual stars so that they are moving independently of each other in the macroscopical field of the whole cluster. In presence of a stellar density gradient, the distribution of the deviations from the mean gravitational field is found to be an anisotropically deformed Holtsmarkian with its maximum shifted to a field deviation vector antiparallel to the density gradient.     

Photon-nucleus scattering and coherent π0 photoproduction in the Δ-hole model

The microscopic Δ-isobar-hole model is applied to the study of photon-nucleus scattering and coherent photoproduction. The role of π and ρ exchange together with additional correlations in the Δ-hole interaction are investigated and compared with the situation in π-nucleus scattering. Because of the transverse photon coupling, the coherent forward propagation of pions, and therefore the strong elastic broadening observed in pion-nuclear scattering, is largely suppressed. The photonuclear processes prove to be sensitive to the medium corrections incorporated through the Δ-self-energies, which are responsible for a strong damping of the reaction cross section. Results are shown for ⁴He and ¹⁶O and compared to the available experimental data.     

Ternäre Verbindungen des Natriums und Kaliums mit CaCu4P2-Struktur

Ternary Compounds of Sodium and Potassium with CaCu₄P₂-type Structure NaCu₄As₂, NaCu₄Sb₂, KCu₄As₂, and KCu₄Sb₂ were prepared and investigated by single crystal methods. They crystallize rhombohedrally and are isotypic to CaCu₄P₂ (space group R3 m). The (hexagonal) lattice constants are By reaction of the same element compositions but alterated conditions six further compounds could be synthesized in the systems Na(K)/Cu(Ag)/P(As, Sb). They crystallize hexagonally, their structure which has not been determined seems to be related to the structure of CaCu₄P₂.     

Sticks and carrots for the design of international climate agreements with renegotiations

This paper examines renegotiations of international climate agreements for carbon abatement. We explore coalition stability under ‘optimal transfers’ that have been suggested to stabilise international environmental agreements (e.g. McGinty in Oxford Economic Papers 59, 45–62, 2007). Such transfer schemes need to be refined when agreements are renegotiated. We determine the requirements that transfers between signatories of an international climate agreement must satisfy in order to stabilise the sequence of agreements that performs best in terms of provision of the public good ‘carbon abatement’. If these requirements are met, no country wants to change its membership status at any stage. In order to demonstrate the applicability of our result we use the STACO model, a 12-regions global model, to assess the impact of well-designed transfer rules on the stability of an international climate agreement. Although there are strong free-rider incentives, we find a stable grand coalition in the first commitment period in a game with one round of renegotiations if renegotations take place sufficiently early.