Proton–proton bremsstrahlung towards the elastic limit at 190 MeV incident beam energy

A series of nucleon–nucleon bremsstrahlung (NNγ) experiments at 190 MeV incident beam energy have been performed at KVI in order to gain more insight into the dynamics governing the bremsstrahlung reaction. After initial measurements wherein the bremsstrahlung process was studied far away from the elastic limit, a new study was used to probe the process nearer to the elastic limit by measuring at lower photon energies. Measured cross sections and analyzing powers are compared with the predictions of a microscopic model and those of two soft-photon models. The theoretical calculations overestimate the data by up to ≈30%, for some kinematics.     

Measurement of the spin and temperature dependence of ddµ molecule formation rate in solid and liquid deuterium

The ddµ molecule formation rate is experimentally measured for the two hyperfine states of the dµ-atom in the temperature range of 5–30 K. Results are consistent with a preliminary measurement by the TRIUMF group and contradict theoretical predictions. The work has been performed on the JINR phasotron (Dubna).     

Range convexity,continuity, and strategy-proofness of voting schemes

A voting scheme assigns to each profile of alternatives reported byn individuals a compromise alternative. A voting scheme is strategy-proof if no individual is better off by lying, i.e., not reporting a best alternative. In this paper the main results concern the case where the set of alternatives is the Euclidean plane and the preferences are Euclidean. It is shown that for strategy-proof voting schemes continuity is equivalent to convexity of the range of the voting scheme. Using a result by Kim and Roush (1984), this leads to characterizations of surjective or unanimous, anonymous, strategy-proof voting schemes.Furthermore, the paper contains an extensive discussion of related results in the area.     

Superfluid3He in high magnetic fields: New results

The superfluid A₁ an A₂ transitions have been studied by means of vibrating wire viscosimeters in magnetic fields up to 9.3 T. Using the technique of quick melting of polarized solid (Castaing-Nozières effect) we have succeeded in increasing the superfluid transition temperature from 2.86 to 3.23 mK, which is the highest up to now. Using this method, with some improvements, it should be possible to test some of the present theoretical models for³He. A minimum of the viscosity in the A₁ phase has been observed for the first time. Very close to the A₂ transition an anomaly in the amplitude of the viscometers seems to indicate the presence of a new phase, or some textural change due to dipole locking.Invited talk at the International Conference on Macroscopic Quantum Phenomena, Smolenice Castle, Czechoslovakia, September 18–22, 1989.The authors wish to thank C. C. Kranenburg and C. M. C. M. van Woerkens for their various contributions to the experiments. Very helpful discussions with K. S. Bedell, B. Castaing, H. Capel, P. Nozières, D. Rainer, A. Schakel, and G. A. Vermeulen are gratefully acknowledged. This work was financially supported by the Stichting voor Fundamenteel Onderzoek der Materie F. O. M.