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James Burridge

Publications and source records attributed to James Burridge.

26 records · Page 2Linked to original sources

Does good memory help you win games?

We present a simple game model where agents with different memory lengths compete for finite resources. We show by simulation and analytically that an instability exists at a critical memory length, and as a result, different memory lengths can compete and co-exist in a dynamical equilibrium. Our analytical formulation makes a connection to statistical urn models, and we show that temperature is mirrored by the agent's memory. Our analysis is easily generalisable to many other game models with implications that we briefly discuss.

nlin.AO↗

The formation and arrangement of pits by a corrosive gas

When corroding or otherwise aggressive particles are incident on a surface, pits can form. For example, under certain circumstances rock surfaces that are exposed to salts can form regular tessellating patterns of pits known as "tafoni". We introduce a simple lattice model in which a gas of corrosive particles, described by a discrete convection diffusion equation, drifts onto a surface. Each gas particle has a fixed probability of being absorbed and causing damage at each contact. The surface is represented by a lattice of strength numbers which reduce after each absorbtion event, with sites being removed when their strength becomes negative. The model generates regular formations of pits, with each pit having a characteristic trapezoidal geometry determined by the particle bias, absorbtion probability and surface strength. The formation of this geometry may be understood in terms of a first order partial differential equation. By viewing pits as particle funnels, we are able to relate the gradient of pit walls to absorbtion probability and particle bias.

cond-mat.stat-mech↗

New families of subordinators with explicit transition probability semigroup

There exist only a few known examples of subordinators for which the transition probability density can be computed explicitly along side an expression for its Lévy measure and Laplace exponent. Such examples are useful in several areas of applied probability, for example, they are used in mathematical finance for modeling stochastic time change, they appear in combinatorial probability to construct sampling formulae, which in turn is related to a variety of issues in the theory of coalescence models, moreover, they have also been extensively used in the potential analysis of subordinated Brownian motion in dimension greater than or equal to 2. In this paper, we show that Kendall's classic identity for spectrally negative Lévy processes can be used to construct new families of subordinators with explicit transition probability semigroups. We describe the properties of these new subordinators and emphasise some interesting connections with explicit and previously unknown Laplace transform identities and with complete monotonicity properties of certain special functions.

math.PR↗

Shocks Generate Crossover Behaviour In Lattice Avalanches

A spatial avalanche model is introduced, in which avalanches increase stability in the regions where they occur. Instability is driven globally by a driving process that contains shocks. The system is typically subcritical, but the shocks occasionally lift it into a near or super critical state from which it rapidly retreats due to large avalanches. These shocks leave behind a signature -- a distinct power--law crossover in the avalanche size distribution. The model is inspired by landslide field data, but the principles may be applied to any system that experiences stabilizing failures, possesses a critical point, and is subject to an ongoing process of destabilization which includes occasional dramatic destabilizing events.

nlin.AO↗

Crossover Behaviour In Driven Cascades

We propose a model which explains how power-law crossover behaviour can arise in a system which is capable of experiencing cascading failure. In our model the susceptibility of the system to cascades is described by a single number, the propagation power, which measures the ease with which cascades propagate. Physically, such a number could represent the density of unstable material in a system, its internal connectivity, or the mean susceptibility of its component parts to failure. We assume that the propagation power follows an upward drifting Brownian motion between cascades, and drops discontinuously each time a cascade occurs. Cascades are described by a continuous state branching process with distributional properties determined by the value of the propagation power when they occur. In common with many cascading models, pure power law behaviour is exhibited at a critical level of propagation power, and the mean cascade size diverges. This divergence constrains large systems to the subcritical region. We show that as a result, crossover behaviour appears in the cascade distribution when an average is performed over the distribution of propagation power. We are able to analytically determine the exponents before and after the crossover.

nlin.AO↗

The Moment Generating function for ray lengths in the Half Gilbert Model with Rectangular Cells

In the full rectangular version of Gilbert's tessellation lines extend either horizontally (with east- and west--growing rays) or vertically (north- and south--growing rays) from seed points which form a Poisson point process, each ray stopping when another ray is met. In the half rectangular version, east and south growing rays do not interact with west and north rays. Using techniques developed in our previous paper, we derive an exact expression for the moment generating function for the ray length distribution in the half rectangular model.

math.PR↗

Cascade sizes in a branching process with Gamma distributed generations

We derive an exact expression for the probability density function of the cascade size (total progeny) in a continuous state branching process when the generations are Gamma distributed. The distribution has application in the modelling of cascade processes such as landslides and electrical network failures.

math.PR↗

Full and Half Gilbert Tessellations with Rectangular Cells

We investigate the ray-length distributions for two different rectangular versions of Gilbert's tessellation. In the full rectangular version, lines extend either horizontally (with east- and west-growing rays) or vertically (north- and south-growing rays) from seed points which form a Poisson point process, each ray stopping when another ray is met. In the half rectangular version, east and south growing rays do not interact with west and north rays. For the half rectangular tessellation we compute analytically, via recursion, a series expansion for the ray-length distribution, whilst for the full rectangular version we develop an accurate simulation technique, based in part on the stopping-set theory of Zuyev, to accomplish the same. We demonstrate the remarkable fact that plots of the two distributions appear to be identical when the intensity of seeds in the half model is twice that in the full model. Our paper explores this coincidence mindful of the fact that, for one model, our results are from a simulation (with inherent sampling error). We go on to develop further analytic theory for the half-Gilbert model using stopping-set ideas once again, with some novel features. Using our theory, we obtain exact expressions for the first and second moment of ray length in the half-Gilbert model. For all practical purposes, these results can be applied to the full-Gilbert model as much better approximations than those provided by Mackissack and Miles.

math.PR↗