Desmond A. Johnston

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We investigate a generalized Ising action containing nearest neighbour, next to nearest neighbour and plaquette terms that has been suggested as a potential string worldsheet discretization on cubic lattices by Savvidy and Wegner. We use both mean field techniques and Monte-Carlo simulations to sketch out the phase diagram. The Gonihedric (Savvidy-Wegner)(More)
We investigate numerically and analytically Potts models on " thin " random graphs – generic Feynman diagrams, using the idea that such models may be expressed as the N → 1 limit of a matrix model. The thin random graphs in this limit are locally tree-like, in distinction to the " fat " random graphs that appear in the planar Feynman diagram limit, N → ∞,(More)
Riparian Management Systems (RiMS) have been proposed to minimize the impacts of agricultural production and improve water quality in Iowa in the Midwestern USA. As part of RiMS, multispecies riparian buffers have been shown to decrease nutrient, pesticide, and sediment concentrations in runoff from adjacent crop fields. However, their effect on nutrients(More)
We study damage spreading in the ferromagnetic Ising model on small world networks using Monte Carlo simulation with Glauber dynamics. The damage spreading temperature T(d) is determined as a function of rewiring probability p for small world networks obtained by rewiring the two-dimensional square and three dimensional cubic lattices. We find that the(More)
Color and black and white line stimulation produce qualitatively and quantitatively different 2-deoxy[14C]glucose column patterns in the striate cortex of macaque monkeys. Microdensitometry of these stimulus-dependent columns reveals interlaminar density differences that serve as a signature for the stimulus conditions which produced them. Such columns are(More)
Motivated by the observation that geometrizing statistical mechanics offers an interesting alternative to more standard approaches, we calculate the scaling behavior of the curvature R of the information geometry metric for the spherical model. We find that R approximately epsilon(-2), where epsilon=beta(c)-beta is the distance from criticality. The(More)
It has been suggested that an information geometric view of statistical mechanics in which a metric is introduced onto the space of parameters provides an interesting alternative characterization of the phase structure, particularly in the case where there are two such parameters, such as the Ising model with inverse temperature beta and external field h.(More)
Four dimensional simplicial gravity has been studied by means of Monte Carlo simulations for some time [1], the main outcome of the studies being that the model undergoes a discontinuous phase transition [2] between an elongated and a crumpled phase when one changes the curvature (Newton) coupling. In the crumpled phase there are singular vertices growing(More)