Causal Entropic Forces, Narratives and Self-organisation of Capital Markets

The intersubjective markets hypothesis is revisited with respect to causal entropic principles. While the financial system is assumed to naturally evolve towards uncertainty, a spontaneous and unstable form of order emerges, thanks to narratives, leading to self-organised criticality. This article also includes a discussion about main hypotheses in finance, about the link between volatility spikes and entropy, and, finally, about the important role of narratives as forms of collective intelligence. JEL: D40, D50, D53, D70, D80

Parcels and particles: Markov blankets in the brain

At the inception of human brain mapping, two principles of functional anatomy underwrote most conceptions – and analyses – of distributed brain responses: namely functional segregation and integration. There are currently two main approaches to characterising functional integration. The first is a mechanistic modelling of connectomics in terms of directed effective connectivity that mediates neuronal message passing and dynamics on neuronal circuits. The second phenomenological approach usually characterises undirected functional connectivity (i.e., measurable correlations), in terms of intrinsic brain networks, self-organised criticality, dynamical instability, etc. This paper describes a treatment of effective connectivity that speaks to the emergence of intrinsic brain networks and critical dynamics. It is predicated on the notion of Markov blankets that play a fundamental role in the self-organisation of far from equilibrium systems. Using the apparatus of the renormalisation group, we show that much of the phenomenology found in network neuroscience is an emergent property of a particular partition of neuronal states, over progressively coarser scales. As such, it offers a way of linking dynamics on directed graphs to the phenomenology of intrinsic brain networks.

Time limited self-organised criticality in the high rate deformation of face centred cubic metals

Plastic deformation is a fundamentally important physical process, ultimately determining how materials can be used. Metal plasticity is governed by dislocation dynamics and lattice twinning. Although many continuum constitutive models exist, plasticity is now known to occur in discrete events arising from the self-organisation of dislocations into ‘avalanches’ under applied stress. Here we extend avalanche plasticity to high strain rates, by introducing time limitation to self-organisation. At high rates large avalanches fail to form; the system must self-organise around new constraints. Various macroscopic consequences include an increasing rate of work hardening with strain rate. We perform new measurements on high purity copper that distinguish between instantaneous and permanent strength contributions across a strength transition at 104 s−1, showing the transition to be a change in structural evolution. Strong model agreement validates our time limited self-organisation approach. Our work results in a unified, physically realistic framework for plasticity, with wide applicability.

Open questions

Four areas requiring further research are introduced and possible PhD projects are identified. They are (i) workhardening, (ii) electroplasticity, (iii) mobility of dislocations and (iv) hydrogen-assisted cracking. In each case the topic is introduced and key questions are identified. Self-organised criticality and slip bands are considered in the discussion of work hardening. The impact of drag forces is considered in the discussionof dislocation mobility. Possible mechanisms for hyfrogen-assisted cracking include hydrogen-enhanced decohesion (HEDE), adsorption-induced dislocation emission (AIDE) and hydrogen-enhanced localised plasticity (HELP).