The next in our series of FraMEPhys Seminars was given by Mark Pexton (Durham) on Monday 3rd June 2019.

Mark’s title was “Contextuality, Emergence and Unification in Physics”.

Abstract: A contextual account of emergence and unification is presented. It is argued that emergent phenomena can be thought of as the consequence of system/context interactions. Contexts often involve modal relations not contained in the first order level of the system in question, hence although the system itself may appear reducible, the combination of system and context is not. Unification as an explanatory strategy can sometimes be seen as linked with reductionist intuitions – by considering their reduction base, disparate systems can be shown to be different manifestations of the same underlying phenomena. However, unifications do not proceed via reduction bases alone. Sometimes they involve moving up a ‘level’ of modal space to unify disparate microphysical phenomena by considering unifying features of the properties of aggregates (such as in universality in critical phenomena). It is argued that unification itself as an explanatory strategy (and therefore putative guide to ontological commitments) is itself highly contextual. Unifications can proceed by shifting the demarcations between systems and contexts to provide new system/context boundaries that create different sets of ‘similar’ unified physical phenomena. As such unification does not easily fit a standard paradigm of reduction or emergence.

There was a reading group with the speaker before the talk. We discussed “Reduction and emergence in the fractional quantum Hall state”, joint work between Tom Lancaster and Mark.