Sigma Club

Whatever else our theories about the natural world are, they ought to be consistent with the evidence produced by our interactions with it – our theories ought to be at least empirically adequate. This is the minimal commitment of empiricism. Yet the central notions of evidence and empirical adequacy have not been satisfactorily elucidated. Prominent accounts of evidence treat it as detachable from the manner in which it was produced. However, considered as detached results, the corpus of empirical evidence appears to be contradictory and discontinuous. Empirically derived parameter values evolve, sometimes radically, over time and the very concepts used to interpret evidence change between epistemic contexts. It would be a fool’s errand to try to make our theories adequate with respect to evidence in this sense. In this talk, I lay the groundwork for a new empiricist philosophy of science by furnishing a non-detached characterization of evidence and an epistemology of empirical adequacy appropriate to it. I illustrate these accounts using case studies from astrophysics and cosmology, including observations of the Hulse-Taylor pulsar, historical observations of supernovae, and the history of measurements of the Hubble parameter.

Philosophers have on occasion noticed various analogies between interpretive approaches to statistical mechanics and quantum mechanics. Probably the most often noted analogy is between the Boltzmannian approach to statistical mechanics and the de Broglie-Bohm approach to quantum mechanics. The possible and pertinent analogies do not end there however. The purpose of this talk is to draw them out in order to see what is suggested about the two theories' interpretation. The main lessons I draw are as follows. First, I claim that there is at least one interpretation available in statistical mechanics which has been so far overlooked and has a natural analogy in the Everettian interpretation of quantum mechanics. Second, I show that to a certain extent the interpretive choices in both theories depend importantly in how stochasticity is interpreted, a point which has not been seriously raised in the literature. Finally, I suggest that pursuing these analogies suggests the possibility of a kind of “measurement problem” in statistical mechanics.

Abstract: Spacetime functionalism, the view that spacetime is as spacetime does, allows for an interesting interpretational perspective on both classical and quantum gravitational theories. In this paper, I'll explore the consequences of a particular kind of spacetime functionalism for a particular variety of non-commutative gravitational theory. The spacetime functionalism I advocate analyses the spacetime concept as a functional one, and…

To quite a few observers outside the field of elementary particle physics, the discovery of the Higgs boson in 2012 appeared to be just the final step in a long series of discoveries and precision tests in which stronger and stronger accelerator experiments had confirmed all particles of the Standard Model (SM) and scrutinized their interactions. The present paper argues that this picture needs qualifications. They provide two important lessons for the role of crucial experiments in a theory-laden context and the operation of epistemic and pragmatic criteria of theory (or model) choice.

As part of his attempt to interpret the foundations of non-relativist quantum mechanics, Hermann Weyl developed a suggestive technique to accommodate aggregates of quantum particles while taking into account these particles’ apparent lack of identity (see Weyl , pp. 237-252, and Weyl ). The technique is suggestive in that it attempts to make sense of the putative restrictions on the applicability of identity in the quantum domain without changing either the underlying logic or the relevant set theory. In this paper, I reconstruct this technique and assess its feasibility, contrasting it with attempts to make sense of the foundations of non-relativist quantum mechanics by jettisoning identity entirely and revising both the underlying logic and the relevant set theory (French and Krause ). I argue that Weyl’s original approach has significant benefits.

Abstract: Traditionally the realist project in quantum theory has taken one of two forms: First, defending one of many different possible interpretations of quantum theory as the one true depiction of reality. Second, defending what has been termed wavefunction realism, according to which ordinary space is an illusion and we in fact live in a 3N-dimensional configuration space, where N…

Attendants may wish to have a look at the related article. Adam Caulton is Associate Professor of Philosophy at the University of Oxford and a Fellow of Balliol College.

In this talk, I will explore several philosophical themes that have recently emerged in the foundations of Newton-Cartan theory (a geometric non-relativistic theory of gravity), especially the status of the theory's "gauge symmetries", the role of symmetry-breaking observer fields in the theory, and the theory's relationship with teleparallel gravity. Part of the material will be based on joint work with Derek Wise and James Read (respectively).

In 1953 A. Grothendieck proved a theorem that he called The Fundamental Theorem on the Metric Theory of Tensor Products. This result is known today as Grothendieck’s inequality (or Grothendieck’s theorem). Originally, it is recognised as one of the major results of Banach space theory. Grothendieck formulated his deep result in the language of tensor norms on tensor products of Banach spaces. To this end he described how to generate new tensor norms from known ones and unfolded a powerful duality theory between tensor norms. Only in 1968, thanks to J. Lindenstrauss and A. Pelczynski Grothendieck’s inequality was decoded and equivalently rewritten – in matrix form – which lead to its global breakthrough

The comparison of geometrical properties of black holes with classical thermodynamic variables reveals surprising parallels between the laws of black hole mechanics and the laws of thermodynamics. Since Hawking’s discovery that black holes when coupled to quantum matter fields emit radiation at a temperature proportional to their surface gravity, the idea that black holes are genuine thermodynamic objects with a well-defined thermodynamic entropy has become more and more popular. Surprisingly, arguments that justify this assumption are both sparse and rarely convincing. Most of them rely on an information-theoretic interpretation of entropy, which in itself is a highly debated topic in the philosophy of physics. Given the amount of disagreement about the nature of entropy and the second law on the one hand, and the growing importance of black hole thermodynamics for the foundations of physics on the other hand, it is desirable to achieve a deeper understanding of the notion of entropy in the context of black hole mechanics. I discuss some of the pertinent arguments that aim at establishing the identity of black hole surface area (times a constant) and thermodynamic entropy and show why these arguments are not satisfactory. I then present a simple model of a Black Hole Carnot cycle to establish that black hole entropy is genuine thermodynamic entropy which does not require an information-theoretic interpretation.

Abstract: Does time have a direction? Intuitively, it does. After all, our experiences, our thoughts, even our scientific explanations of phenomena are time-directed: things evolve from earlier to later, and it would seem unnecessary and indeed odd to try to expunge such talk from our philosophical lexicon. Nevertheless, in this talk I will make the case for what I call…

I discuss the debate between advocates of dynamical versus geometrical approaches to spacetime theories, in the context of both special and general relativity. By distinguishing between what I call ‘individual’ versus ‘modal’ constraints, I argue—pace e.g. Brown—that there exists available a perfectly viable form of the geometrical approach.

First I will argue for the inevitability of a coherent, non-circular system of operational definitions of the basic spatiotemporal quantities, in terms of which the empirically testable spatiotemporal statements of physics should be expressed. A few examples will illustrate that the task is not trivial, especially if the definitions should hold with high, relativistic, precision. In my talk, I will outline a possible construction of such a system of operational definitions. It will be seen that the complete collection of operational definitions, by means of which one can reconstruct something similar to our usual spatiotemporal intuitions, would require the satisfaction of certain conditions. Whether these conditions are satisfied is an empirical question which has never truly been examined. Some speculative considerations show however an interesting picture. If all conditions are empirically satisfied then the resulted spacetime structure is a Minkowski geometry. If however, as it is expected, some of the important conditions are violated, it is not at all obvious what the resulted spacetime structure is. Nevertheless, straightforward generalizations of Minkowski geometry offer themselves as suitable mathematical description of the empirically ascertained spacetime structure; more straightforward than Riemannian geometry on a four-dimensional manifold.

A physical theory is a partially interpreted axiomatic formal system (L, S), where L is a formal language with some logical, mathematical and physical axioms, and with some derivation rules, and the semantics S is a relationship between the formulas of L and some states of affairs in the physical world. In our ordinary discourse, the formal system L is regarded as an abstract object or structure, the semantics S as something which involves the mental/conceptual realm. This view is of course incompatible with physicalism. How can physical theory be accommodated in a purely physical ontology? The aim of the talk is to outline an account for meaning and truth of physical theory, within the philosophical framework spanned by three doctrines: physicalism, empiricism, and the formalist philosophy of mathematics.