Cluster algorithms for anisotropic quantum spin models

We present cluster Monte Carlo algorithms for theXYZ quantum spin models. In the special case ofS=1/2, the new algorithm can be viewed as a cluster algorithm for the 8-vertex model. As an example, we study theS=1/2XY model in two dimensions with a representation in which the quantization axis lies in the easy plane. We find that the numerical autocorrelation time for the cluster algorithm remains of the order of unity and does not show any significant dependence on the temperature, the system size, or the Trotter number. On the other hand, the autocorrelation time for the conventional algorithm strongly depends on these parameters and can be very large. The use of improved estimators for thermodynamic averages further enhances the efficiency of the new algorithms.     

A three carbon homologation by the ring-opening of β-propiolactones with diorganocuprates

Various organocuprates react with β-propiolactones to give β-substituted propionic acids in high yields.     

Production of direct single electrons in proton-nucleus collisions at 13 GeV/c

Direct production of single electrons in proton-nucleus collisions at 13 GeV/c has been measured. A rising $\text{e}\text{π}$ ratio with decreasing p_T above the 10^?4 level is observed for low p_T single electrons. The source of the rising $\text{e}\text{π}$ ratio at low $\text{e}\text{π}$ ratio at low p_T is discussed in connection with the low mass dielectron continuum below the ? mass region.