Statistical mechanics of voting

Decision procedures aggregating the preferences of multiple agents can produce cycles and hence outcomes which have been described heuristically as `chaotic'. We make this description precise by constructing an explicit dynamical system from the agents' preferences and a voting rule. The dynamics form a one dimensional statistical mechanics model; this suggests the use of the topological entropy to quantify the complexity of the system. We formulate natural political/social questions about the expected complexity of a voting rule and degree of cohesion/diversity among agents in terms of random matrix models---ensembles of statistical mechanics models---and compute quantitative answers in some representative cases.Comment: 9 pages, plain TeX, 2 PostScript figures included with epsf.tex (ignore the under/overfull \vbox error messages

Recent Performance of the NPTC Equipment Compared with the Clinical Specifications

The construction of the Northeast Proton Therapy Center (NPTC) at Massachusetts General Hospital is nearing completion. Preliminary beam tests have begun and clinical acceptance testing is soon to follow. Preliminary measurements have been made to determine the properties of the system as compared to the clinical requirements. These results will be discussed. The procedures and instrumentation to be used for testing will also be described