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Durham University

Institute of Advanced Study

Past Events

IAS Fellow's Public Lecture - What Characterizes Emergence in Physics?

6th November 2014, 17:30 to 18:30, Sir James Knott Hall, Trevelyan College, Professor Margaret Morrison (University of Toronto)

Emergent phenomena are typically described as those that cannot be reduced, explained nor predicted from their constituent parts or microphysical base. Emergence is also defined as the way complex systems and patterns arise out of a multiplicity of relatively simple interactions (Wiki). Many debates about emergence focus on the nature of human consciousness and its relation to brain states, specifically, whether the former can be reduced to the latter, or whether consciousness can even be considered something “physical”. However, there are many other areas where emergence is just as important – physics, social networks, financial markets, biological systems and many more. What this seems to suggest is that much of what we experience in the world is emergent. But can this be right? What does it mean to “arise from” something but not be reducible to it or explained by it? One way of answering this question is to simply say that emergence is merely an epistemic notion pointing to a gap in our knowledge of these phenomena. By contrast, Philip Anderson’s famous (1972) claim that the whole in not only greater than but very “different from” its parts implies a strong ontological or physical dimension to emergence, one that requires us to explain how macro properties characteristic of emergence can be physically distinct from the micro properties from which they emerge.

In this lecture Professor Margaret Morrison examines various ways of thinking about emergence in the context of different examples. She claims that despite the ambiguity and mysterious nature of emergence it can be understood in a systematic way using a mathematical technique called renormalization group (RG) methods to illustrate how the ‘universal’ characteristics of emergent phenomena, stable macro behavior that demarcates a property as emergent (superconductivity, magnetism, etc), are actually insensitive to the underlying microphysics. Interestingly, RG methods are used not only in physics but also in financial markets, making them the prime candidate for understanding emergence. Although RG methods are closely related to the way systems exhibit different “scaling” behavior it is important to stress that the independence associated with emergent phenomena are not simply a reflection of the fact that different ‘levels’ are appropriate when explaining behavior, e.g. we needn’t appeal to the quantum level when we want to build a bridge and we don’t appeal to a particular individual’s behaviour in explaining the operation of financial markets. Her talk attempts a resolution to this problem of physical independence by showing how a closer examination of RG methods can provide a way of explicating the relation between micro and macro properties, a relation that satisfies the requirements for explaining emergence.

Lecture is open to all and free to attend.

Details about Professor Margaret Morrison

Directions to Trevelyan College

Map - Trevelyan College is denoted as building No: 9

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