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• Stuart Bartlett

I am interested in using the methods of statistical mechanics in an attempt to formulate a general theory of evolution, applicable to all physical and chemical systems (biological systems being a special, highly complex case of the latter). We can observe evolution among self-organised structures in simple physical systems but notions of fitness and adaptability are undefined in this context. How might we predict the properties of pattern-forming, self-organised systems from physical considerations?

In my view, evolution occurs at all levels from the inter-molecular, sub-cellular level to the group level. Hence viewing evolution only in terms of the mutations of strings of DNA which control the survivability of individual organisms misses a considerable part of the picture. But characterising and predicting evolution from physical principles is a more than formidable proposition.

Nevertheless it may be possible to make some macro level predictions about non-equilibrium systems if a suitable mathematical framework was available. Maximum entropy production is one such idea but opinions currently differ as to whether it represents a physical principle or just an information theoretic device.

Life appears to be some kind of complex critical phenomenon which is fundamentally dependant on a thermodynamic regime poised in the nomansland (or not) between complete order and complete chaos. At the characteristic length scales of life on Earth, information storage becomes difficult at very high temperatures since correlations between particles and their motions diminish. On the other hand, at low temperatures information storage might be possible but chemical or physical change happens so rarely that life as we know it could not function. Additionally, life depends on disequilibrium. Without flows of free energy and materials life also has no meaning. So life is clearly a non-equilibrium critical phenomenon in which complex patterns of matter and energy flow arise and allow information to be gleaned from the surrounding environment. But how is it that such flows can persist for so long and be so robust to perturbations? Why is it that they arose so early in our planet's history, as if life is a natural state of matter under certain conditions, rather than just being very lucky? Did they organise themselves to a critical state or are they only possible in systems which are already close to or at criticality?

In my PhD I hope to attempt to answer a small fraction of these rather large questions using a combination of statistical mechanics (including self-organised criticality, the maximum entropy production principle) and numerical modelling.

Working with...

Seth Bullock Professor, Electronics and Computer Science (FPAS)

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