Sigma Club

Abstract: Collapse models are modifications of quantum theory where the wave function is treated as physically real and the collapse of the wave function is a physical process. This appears to introduce a time reversal asymmetry into the dynamics of the wave function since the collapses affect only the future state. We challenge this conclusion, showing that if the physically…

Abstract. According to the present state of knowledge, the Universe in small scales is described by the laws of quantum theory. On the other hand, the fundamental theory of gravity is believed to be Einstein's relativity. Its effects become relevant when we consider large masses or (equivalently) large energies. One of the main features of Einstein's theory is the fact…

To avoid paradox, I maintain that two simple tensed conditionals are true: (i) if the atom has decayed then the cat is dead; (ii) if the atom has not decayed then the cat is alive. So long as it is true at some time that the atom decays then it follows from tense logic (under mild constraints) that at all…

Abstract: In Boltzmannian statistical mechanics macro-states supervene on micro-states. This leads to a partitioning of the state space of a system into regions of macroscopically indistinguishable micro-states. The largest of these regions is singled out as the equilibrium region of the system. What justifies this association? We review currently available answers to this question and find them wanting both for…

Standard approaches to the interpretation of physical theories require a structurally unambiguous characterization of the models of a theory. In this talk I argue that the nature of the empirical support for quantum field theory does not warrant commitment to one particular type of structure as constitutive of the theory. Rather, the empirical adequacy of some models of the theory…

Abstract: The canonical formalism of general relativity affords a particularly interesting characterisation of the infamous hole argument. It also provides a natural formalism in which to relate the hole argument to the problem of time in classical and quantum gravity. In this paper I will examine the connection between these two much discussed problems in the foundations of spacetime theory…

Abstract: The conflict between an objective passage of time and relativistic physics is sometimes summed up as follows: first, relativistic physics implies a ‘B-theoretic’ or ‘block universe’ view of time, and second, the B-theory implies that there is no objective passage. Here, I’ll take issue with the second entailment claim. I begin by presenting the case for veridicalism, the claim…

Abstract: TBA

Abstract: This talk proposes to re-examine the parity-of-reasoning or double-standard fallacy argument, which favours a time-symmetric Gold universe model over a cosmological arrow of time. There are two reasons for this re-examination. One is empirical: 1) the recent discovery of an expanding and accelerating universe questions the symmetry assumption of the Gold universe on empirical grounds; 2) the other is…

Abstract: This article develops a model-based account of the standardization of physical measurement, taking the contemporary standardization of time as its central case study. To standardize the measurement of a quantity, I argue, is to legislate the mode of application of a quantity concept to a collection of exemplary artefacts. Legislation involves an iterative exchange between top-down adjustments to theoretical and…

The syntactic approach to physical theories was and is unpopular for reasons which have much more to do with the limitations of first order logic than any fundamental philosophical deficiencies of the position itself … #SigmaClub

The proof of the godel theorems is notoriously difficult to understand. We present a simplified version using sorites arithmetic which is much easier to follow. #SigmaClub

Sebastian de Haro is a Senior lecturer in theoretical physics at the Amsterdam University College (AUC) and the Faculty of Science of the University of Amsterdam. His 2001 PhD in physics was under Gerard 't Hooft, and he is currently pursuing a PhD in Philosophy at Cambridge under Jeremy Butterfield. #SigmaClub

Discussions of physical ontology often come down to two basic options. Either the basic physical entities are particles, or else they are fields. James Owen Weatherall will argue that, in fact, it is not at all clear what it would mean to say that the world consists of fields.

Two approaches to understanding the idealizations that arise in the Aharonov-Bohm (AB) effect are presented. It is argued that the standard topological approach, which takes the non-simply connected electron configuration space to be an essential element in the explanation and understanding of the effect, is flawed.