Dean Rickles

A simple guide to chaos and complexity

The concepts of complexity and chaos are being invoked with increasing frequency in the health sciences literature. However, the concepts underpinning these concepts are foreign to many health scientists and there is some looseness in how they have been translated from their origins in mathematics and physics, which is leading to confusion and error in their application. Nonetheless, used carefully, “complexity science” has the potential to invigorate many areas of health science and may lead to important practical outcomes; but if it is to do so, we need the discipline that comes from a proper and responsible usage of its concepts. Hopefully, this glossary will go some way towards achieving that objective.

Mirror Symmetry and Other Miracles in Superstring Theory

The dominance of string theory in the research landscape of quantum gravity physics (despite any direct experimental evidence) can, I think, be justified in a variety of ways. Here I focus on an argument from mathematical fertility, broadly similar to Hilary Putnam’s ‘no miracles argument’ that, I argue, many string theorists in fact espouse in some form or other. String theory has generated many surprising, useful, and well-confirmed mathematical ‘predictions’—here I focus on mirror symmetry and the mirror theorem. These predictions were made on the basis of general physical principles entering into string theory. The success of the mathematical predictions are then seen as evidence for the framework that generated them. I shall attempt to defend this argument, but there are nonetheless some serious objections to be faced. These objections can only be evaded at a considerably high (philosophical) price.

Causality in complex interventions

In this paper I look at causality in the context of intervention research, and discuss some problems faced in the evaluation of causal hypotheses via interventions. I draw attention to a simple problem for evaluations that employ randomized controlled trials. The common alternative to randomized trials, the observational study, is shown to face problems of a similar nature. I then argue that these problems become especially acute in cases where the intervention is complex (i.e. that involves intervening in a complex system). Finally, I consider and reject a possible resolution of the problem involving the simulation of complex interventions. The conclusion I draw from this is that we need to radically reframe the way we think about causal inference in complex intervention research.

Econophysics and the Complexity of Financial Markets

Publisher Summary This chapter presents the central ideas of econophysics: to show where they come from (their motivations), and to show how it all fits in with complex systems science. Physics-based approach (i.e. econophysics) is an approach generally couched in the language of statistical physics. Statistical physics is a framework that allows systems consisting of many (possibly heterogeneous) particles to be rigorously analyzed. In econophysics, these techniques are applied to “economic particles,” namely investors, traders, and consumers. Markets are then viewed as (macroscopic) complex systems with an internal (microscopic) structure consisting of many of these “particles” interacting so as to generate the systemic properties (the microstructural components being “reactive” in this case resulting in an adaptive complex system relative to another system, or the environment). Further, discussion restricts attention to financial markets since that is where most work in econophysics has been conducted, on account of the availability of copious amounts of high-frequency data. Indeed, at the root of most of the work carried out in econophysics is a family of “stylized facts” (empirically observable universal generalizations) that are to be found in this economic data. Econophysicists seek to find new instances of such facts and to explain these and previously known stylized facts using physics-inspired techniques and models, with the ultimate aim of providing these facts with a theoretical basis.

Chapter 7 Who's Afraid of Background Independence?

Background independence is generally considered to be ‘the mark of distinction’ of general relativity. However, there is still confusion over exactly what background independence is and how, if at all, it serves to distinguish general relativity from other theories. There is also some confusion over the philosophical implications of background independence, stemming in part from the definitional problems. In this chapter I attempt to make some headway on both issues. In each case I argue that a proper account of observables goes a long way in clarifying matters. Further, I argue, against common claims to the contrary, that the fact that these observables are relational has no bearing on the debate between substantivalists and relationalists, though I do think it recommends a structuralist ontology, to as I endeavour to explain.

Time, Observables, and Structure

In this chapter I consider what recent work on background independent physics can do for structuralism, and what structuralism can do for background independent physics. I focus on the problems of time and observables in gravitational physics. The ‘frozen’ character of the observables of general relativity is usually considered to constitute a serious problem for the theory. I argue that by invoking correlations between physical quantities we can provide a natural explanation of the appearance of time and change in timeless structures. I argue that this response can resolve a problem with Max Tegmark’s ‘extreme structuralist’ position. I then consider what bearing the mathematical representation used (namely Rovelli’s framework of ‘partial’ and ‘complete’ observables) has on the debate over the nature of structure in discussions of structural realism (i.e. the question of how structures are to be conceived). I argue that it has both the resources to ground the notion of structure in physics and to answer the ‘no relations without relata’ objection.

Quantum Gravity Meets &HPS

Quantum gravity research constitutes an ideal and novel historical episode that should appeal to historians, philosophers, and sociologists of science alike. The absence of possible experiments and experimental anomalies that usually drive the development of the field expose an entirely different set of inner workings than we are used to seeing in science. One can see how a range of virtues (such as unification, beauty, and so on) beyond “the usual suspects” can guide both the construction and justification of theories. One also sees the strong role played by analogies, which continued to be pursued despite the knowledge that the analogy was far from perfect. Methodologically, what the development of quantum gravity reveals is that what is deemed appropriate will depend upon what constraints are available at the time, and this is prone to changes of a great variety of sorts. I have argued that the framework of constraints provides a useful tool with which to prise open the black box that contains the development of quantum gravity. However, quantum gravity itself provides a tool with which to see the operation and evolution of theoretical constraints that are often overpowered by experimental constraints.

A Participatory Future of Humanity

History is rich with examples of humans expecting future generations to deal with their mess (be it debts, environmental impacts, or whatever); this can include people taking from their own future selves. The larger problems of humanity are, I argue, but scaled up versions of this same curious, irrational behaviour. Humanity’s steering of the future must involve going beyond humanity in some sense. The solution I outline in this paper involves a modification of the everyday human stance towards future events and future selves. It involves a (practical, day-to-day) denial. Using a range of examples from physics, philosophy, neuroscience and psychology, ultimately advocates an intervention indicating how actions now are linked to future experiences and events, that agents themselves will have and influence by direct creation. This might seem blindingly obvious, yet the vast majority of humans act as if their lives are determined by the whims of the future. If humans fully realised how tightly bound they are to their future conscious life and experiences (and others’), and how that life and experience is a direct extension of their life and experience right now (so that actions can be seen to have direct consequences for their present selves: those that are experiencing right now), then they will be far more responsible in choosing their actions.

History and Mythology

This opening chapter considers the orthodox story of string theory’s genesis, and indicates how it might be refined. We describe the broad outlines (or ‘periodisation’) of the history as presented in this book. We also include a brief guide to the physics and mathematics of vibrating strings and string theory, showing their similarities and differences.

Interdisciplinary perspectives on the flow of time

Where does the study of the flow of time belong: physics, the cognitive sciences, philosophy, or somewhere else? Physicists and philosophers have set themselves up into two camps: those who believe there is genuine flow or becoming in the world and those who believe there is just a block of events. What had not been considered is whether the subjective feeling of flow of time is the same the world over, whether it could be tampered with by brain injury, or whether it is present at all developmental stages. We lay out the problem, explain terms, and provide synopses of relevant ideas.