9713977 Young This grant supports the continuing work of a senior PI, distinguished for his significant contributions to the numerical analysis of several problems in statistical mechanics. In the present grant he is planning to conduct theoretical studies of quantum phase transitions in random magnetic systems. These problems can be solved using sophisticated, state-of-the-art numerical techniques. The principal objectives are to: (1) search for universal critical behavior at the quantum transition and (2) to investigate the characteristic paramagnetic phase singularities, called the Griffiths-McCoy singularities. %%% Most phase transitions are classical, i.e. the phase transitions takes place at temperatures which are high compared to when the quantum mechanical effects become important in a given system. And yet, the transition temperatures can be reduced by introduction of disorder. Given the ease in studying material properties at low temperatures, it is conceivable that novel transitions may be strongly quantum in nature. The combination of quantum and disorder provides a framework which is both complex and has not been studied well before. This senior PI plans to carry out a numerical study, to lead to an understanding of what to expect in a quantum phase transition in the presence of strong disorder. ***
