RESEARCH

Records of the past are a pervasive feature of our world that are used in many areas of both physics and philosophy, but out best account of records is overidealised and leaves many questions unanswered. I will present a new account of records in terms of robustness against noise. This account highlights previously overlooked features of records: their use of redundancy and their reliance on techniques common in the physics of macroscopic phenomena, such as coarse-graining. These features have implications for how we explain the record asymmetry through statistical mechanics as well as for related debates such as that surrounding Maxwell's demon.

Quantum darwinism explains the emergence of classicality using records formed in the environment which allow multiple observers to verify the state of a system. However exactly what it aims to derive is unclear and it's use of observers is overemphasised, this has lead to a number of criticisms. I will show that focusing on what a record is in a general sense helps set a standard for classicality that quantum darwinism can aim for and that this need not involve any actual observers. This standard can also be used to show how emergence in quantum darwinism relates to philosophical accounts of emergence which focus on dynamical laws. Currently quantum darwinism's information theoretic framing make it difficult to apply these accounts of emergence.

There are two main types of approach to interpreting the quantum state; either focusing on the fundamentality of the quantum state - a wavefunction or state realist view - or on how projection operators represent properties - an observable-first approach. Rather than being incompatible, I argue that these correspond to taking a 3rd person and 1st person perspective respectively. I also argue that the 1st person perspective, along with metaphysical indeterminacy (which is a integral part of how the 1st person, observable-first approach attributes properties to quantum systems), is ineliminable for the way that the metrology literature, as well as the work of Bohr, characterises measurement through the properties of a system. Finally, I show how the 1st person, observable-first approach can emerge in the world through the process of decoherence, hence showing the compatibility of the two approaches.

One way to interpret the difference between presentism and eternalism is perspectively. This suggestion, from Savitt (2006), argues that from a perspective outside of time the world is eternalist, and from a perspective embedded within time the world is presentist. In this paper, I develop what it means to be in an embedded, presentist perspective and connect this to the hypothesis that the future is metaphysically open. Openness comes down to failures of predictability. I then connect this to practical limits on prediction that come from being in an embedded presentist perspective, such as the lightcone structure of spacetime and being embedded at emergent levels of reality. Understood in this way, the presentist perspective offers a powerful way to explain the explanatory success of theories such as statistical mechanics which often use local, semi-isolated subsystems as well as emergent probabilities. It also provides a new way of thinking about the accusations that thermodynamics, and its statistical underpinnings, is subjective or epistemic.

I argue that we should understand the flow of time using three ideas: information, emergence, and perspectives. Doing so produces an account that has a strong naturalistic basis but focuses on the emergent level of reality that is closely linked to our experience of time. I will develop a metaphysical account of time’s flow that defines it as the localised becoming of events and argue that this should be understood via a perspectival ontology. From inside of time the world is presentist and from the outside it is eternalist. I will show that the internal perspective, along with the open future and fixed past, is an essential element of physics despite common assumptions that physics is perspective independent. Evidence for this will be found by looking at the role that information, in particular records of the past, plays in physics and showing how this is an important factor in how we understand and interpret theories such as thermodynamics and quantum mechanics. I analyse a number of these instances and provide new ways of thinking about how they use information.