Physics and Computation

September 7-11th 2009
Ponta-Delgada, Azores, Portugal

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August 03, 2009, at 02:22 PM by -
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Talk from Ben de Lacy Costello


Computing using the BZ reaction - collision based gates to glider gun like structures


The interactions of two or more excitation pulses can be interpreted in terms of collision based computing. In experiments with the Belousov Zhabotinsky reaction we show that a number of collision types occur as previously predicted by theoretical modelling. In our approach the collisions of small excitation pulses occur in a sub-excitable zone within the chemical reactor. Therefore, once fragments enter this zone there is no external control of trajectory etc. and the collision based gates implemented via their interaction of fragments can be considered an architectureless computation. From an architectureless system we describe wave transfer through a highly structured network of light and dark cells. The chemical diode is well established where altering the geometry and excitability of the chemical substrate (diode) can selectively control wave transfer across a single junction. By creating a network of light (non excitable) and dark (excitable) cells we establish a network of diode like junctions between excitable cells. If the excitability of the network is reduced then junction failures occur leading to spiral formation within the network. The trajectories of the intial spirals are locked around non-excitable areas. These spirals spontaneously degenerate to form multiple interacting spirals. Under specific network conditions spirals trapped within single excitable cells can occur. Depending on network conditions these spirals emit high frequency wave trains along upto four possible diagonal trajectories. However, the spirals do not have stable trajectories within the cell leading to intermittent "firing" of these wave trains. We have observed the formation of these high frequency spirals in both experiment and theoretical models. We have studied the interaction of these high frequency streams in terms of computation for example the interaction of these "glider gun" like structures can lead to the formation of chemical switches and methods of implementing memory. However, most significant is that these structures can provide a constant source of wave generation which can be used in constructing complete sets of logical gates.

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