Projects in Progress

The Toll of the Tolman Effect: On the Status of the Classical Temperature in General Relativity (Joint work with Craig Callender) (draft available upon request!)

The Tolman effect seems to suggest that a system in thermodynamic equilibrium, extended over a region of varying gravitational potential, exhibits a temperature gradient. This seems to run contrary to classical thermodynamics, and raises questions about how to interpret it, questions that we think philosophers of physics have not considered seriously to date. We make four claims. Firstly, we argue that, contrary to much of the contemporary literature on the Tolman effect, it was Einstein -- not Tolman -- who first argued for the Tolman effect. Secondly, we argue that the standard interpretation of the Tolman effect, in terms of `local temperature', leads to the breakdown of much of classical thermodynamics. Thirdly, we argue that Einstein's preferred interpretation in terms of the `wahre Temperatur' -- what we'll call global temperature -- rescues thermodynamics at the cost of local inaccessibility and a lack of contact with phase transitions. Finally, the Tolman effect is often interpreted in terms of redshift, which is itself interpreted in terms of energy and how it gravitates. While many, including Einstein's derivations, have adopted such an interpretation, we provide an alternative interpretation in terms of the general inability, in general relativity, to find local clocks which extend indefinitely far away without distortion -- they slow down because of metric variations. This leads us to propose a third, novel, option with connections to a proposal of Einstein's elsewhere, which we'll call the `wahre-local temperature'. On this view, temperature -- and thermodynamics -- is defined only in relation to local clocks and only to the extent that metric variations can be ignored.  

Putting Pressure Under Pressure: On the Status of the Classical Pressure in Relativity (under review, draft available upon request!)

Much of the century-old debate surrounding the status of thermodynamics in relativity has centered on the search for a suitably relativistic temperature; recent work by Chua (2023) has suggested that the classical temperature concept – consilient as it is in classical settings – ‘falls apart’ in relativity. However, these discussions have still tended to assume an unproblematic Lorentz transformation for – specifically, the Lorentz invariance of – the pressure concept. Here I argue that, just like the classical temperature, the classical concept of pressure breaks down in relativistic settings. This situation suggests a new thermodynamic limit – a ‘rest frame limit’ – without which an unambiguous thermodynamic description of systems does not emerge. I end by briefly discussing how thermodynamics, in requiring preferred frames, bears on the idea of so-called symmetry-to-reality inferences.



Relativistic Locality from Electromagnetism to Quantum Field Theory (Joint work with Chip Sebens (invited contribution to an OUP collected volume on Many-Worlds Interpretations and Locality, edited by Alyssa Ney, preprint available here: https://arxiv.org/abs/2412.11532) 

Electromagnetism is the paradigm case of a theory that satisfies relativistic locality.  This can be proven by demonstrating that, once the theory’s laws are imposed, the state of a region fixes what happens in a certain portion of the future: the contracting light-cone with that region as its base.  The Klein-Gordon and Dirac equations meet the same standard.  We show that this standard can also be applied to quantum field theory (without collapse), examining two different ways of assigning states (reduced density matrices) to regions of space.  Our preferred method begins from field wave functionals and judges quantum field theory to be local.  Another method begins from particle wave functions (states in Fock space) and leads to either non-locality or an inability to assign states to regions, depending on the choice of creation operators.  We take this analysis of Everettian (no collapse) quantum field theory to show that the many-worlds interpretation of quantum physics is local at the fundamental level.  We argue that this fundamental locality is compatible with either local or global (non-local) accounts of the non-fundamental branching of worlds, countering an objection that has been raised to the Sebens-Carroll derivation of the Born Rule from self-locating uncertainty.

Check, Please: De-Idealizing De-Idealizations with Asymptotic Reasoning (Joint work with Yichen Luo, under review, draft available upon request!)

This paper brings together two questions. On the one hand, there is a question of how approximations relate to idealizations. On the other hand, there is a question of whether de-idealization is needed for justified use of --- for `checking' --- idealizations. We propose a generalized account of asymptotic reasoning which answers both questions. On this view, idealizations and approximations are both steps in the general process of asymptotic reasoning, which we understand broadly in terms of the search for stable convergence between models. Furthermore, while stable convergence is often cashed out in the literature in terms of formal approximation schemes and Galilean de-idealizations which `adds back' all the relevant details and brings us back to the ``full representation", we show that such an understanding of stable convergence is itself idealized. We propose three ways of de-idealizing de-idealization, in terms of intra-model, inter-model, and measurement de-idealizations. This highlights ways in which idealizations can be `checked' without appealing to Galilean de-idealizations, which in turn provides us with an understanding of stable convergence in line with scientific practice in physics.



Physical Coherence and Time's Emergence (under review, draft available upon request!)

It is often said that time vanishes in quantum gravity. One general approach to quantum gravity accepts this fundamental timelessness but seeks to derive time's emergence at a non-fundamental level. To better assess such approaches, I develop the criterion of physical coherence and situate it in context by applying it to two programs for time's emergence, drawing from recent works by Chua and Callender (2021) and Chua (forthcoming): semiclassical time and thermal time. Unlike some recent arguments for the metaphysical incoherence of time's emergence, which rule out all claims of time’s emergence `from on high' once we’ve fixed a definition of metaphysical emergence, my criterion of physical coherence leaves open the possibility that some programs in quantum gravity may succeed on their own terms in providing a physically coherent derivation of time from no-time. This sets a challenge for proponents of time's emergence to clarify the conceptual foundations of their program, while at the same time acting as a litmus test for a program's success.

The Problem of Atypicality in LLM-Powered Psychiatry (draft available upon request!)

Large language models (LLMs) are being considered for use in the outpatient psychiatric context for a variety of reasons, to do with public health and access. However, given the target audience — patients with possible psychiatric disorders — the application of LLMs should merit caution. Here we develop a particular problem for LLM-powered psychiatry, which we call the problem of atypicality. We distinguish this problem from the well-known problem of hallucinations. While the latter focuses on the question of the truth or falsehood of LLM outputs, the problem of atypicality is a problem concerning appropriateness of LLM outputs. The problem arises because of the mismatch between LLMs aiming to generate outputs appropriate for typical users, and users who may be atypical relative to the general population. We examine the extent to which technical solutions such as fine-tuning can reduce this problem, and propose recommendations for accommodating this problem.