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- D. A. Johnston
- 2008

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)

- D A Johnston, P Plecháč
- 1997

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)

- D A Johnston, M A Fernando
- Parasitology research
- 1995

The genetic relatedness of 5 Eimeria spp. of the domestic fowl, including 11 strains of E. acervulina, 2 strains of E. tenella and 1 precocious line of E. acervulina, was assayed by means of random amplified polymorphic DNA (RAPD) and denaturing gradient-gel electrophoresis (DGGE). Seven different oligonucleotides were used to generate similarity… (More)

- D A Johnston, M A Fernando
- Parasitology research
- 1997

Electrophoretic variation of enzymes in five Eimeria spp. of the domestic fowl, including nine strains, ten single-sporocyst clones and two single-sporozoite clones of E. acervulina, three strains each of E. maxima and E. tenella, two strains of E. praecox and one strain of E. necatrix, were assayed using cellulose acetate electrophoresis. Ten enzymes… (More)

- Pontus Svenson, Desmond A Johnston
- Physical review. E, Statistical, nonlinear, and…
- 2002

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)

A method of " blocking " triangulations that rests on the self-similarity feature of dynamically triangulated random manifolds is proposed and used to define the renormalization group for random geometries. As an illustration, the idea is applied to pure euclidean quantum gravity in 2d. Generalization to more complicated systems and to higher… (More)

- W Janke, D A Johnston, R Kenna
- Physical review. E, Statistical, nonlinear, and…
- 2003

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)

- Brian P Dolan, D A Johnston
- Physical review. E, Statistical, nonlinear, and…
- 2002

It is known that the exact renormalization transformations for the one-dimensional Ising model in a field can be cast in the form of the logistic map f(x)=4x(1-x) with x a function of the Ising couplings K and h. The locus of the Lee-Yang zeros for the one-dimensional Ising model in the K,h plane is given by the Julia set of the logistic map. In this paper… (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)

We report on single-cluster Monte Carlo simulations of the Ising, 4-state Potts and 10-state Potts models on quenched ensembles of planar, tri-valent (Φ 3) random graphs. We confirm that the first-order phase transition of the 10-state Potts model on regular 2D lattices is softened by the quenched connectivity disorder represented by the random graphs and… (More)