Sigma Club Seminar by Dominic Ryder (LSE Philosophy)
Title: Deidealizing Black Hole Evaporation; a case study in the large-scale structure of deidealization
Abstract: Recent work in the philosophy of the semi-classical gravity has argued that certain paradoxes arise in the modelling of black hole evaporation. Ryder (forthcoming) has argued that canonical derivations of the Hawking effect involve a paradoxical use of stationary spacetimes, and Chua (2025) has argued that a class of derivations of the backreaction of Hawking radiation on the black hole involve a problematic use of asymptotically flat spacetimes. In this paper I investigate the ‘deidealization’ of these apparently problematic models by analysing the justification of the idealizations used. I introduce a distinction between two types of justification: type A involves showing the models draw the correct conclusions despite the idealizations, while type B involves showing why the idealizations used don’t lead to the wrong conclusions. I argue that in all four cases (types A and B for separately backreaction and Hawking radiation arguments) the proposed deidealization requires the large-scale structure of induction, as discussed by Norton (2024). I discuss a sense I which this may generalise to an important form of scientific inference, which I call the large-scale structure of deidealization. Situating the justification of idealizations within the large-scale structure of induction leads to the verdict that the paradox presented in Ryder (forthcoming) is more pernicious than that presented in Chua (2025). Finally, I suggest how the lessons of this case study are important for the epistemology of physics beyond the reach of experimental confirmation.
Dominic Ryder is a PhD student in the Department of Philosophy, Logic and Scientific Method at London School of Economics & Political Science. He is a philosopher of physics and science, interested in modern physics and its epistemology. He studies how idealizations affect the knowledge we can extract from models in domains for which we lack empirical evidence. His research has so far focused on Hawking radiation and the use of idealized models in the framework of quantum field theory in black hole spacetimes, and it has implications for the epistemic status of black hole evaporation, the black hole information paradox and quantum gravity. He has further research interests in the philosophy of sex, sexuality and gender, and formal social epistemology.
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