Sigma Club

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.

Extracting predictions from cosmological theories that describe a multiverse, for what we are likely to observe in our domain, is crucial to establishing the validity of these theories. One way to extract such predictions is from theory-generated probability distributions that allow for selection effects – generally expressed in terms of assumptions about anthropic conditionalization and how typical we are. In this talk, I urge three lessons about typicality in multiverse settings.

Is there a role for computers in the formulation of scientific concepts? Scientific discovery can take various forms: direct observational discovery, finding empirical rules, and discovery of theories. I will begin by considering the roots of scientific discovery and the basic nature of (human) discovery processes. I will then survey methods and associated applications in computational scientific discovery, covering: massive systematic search within a defined space; rule-based reasoning systems; classification, machine vision and related techniques; data mining; finding networks; evolutionary computation; and automation of scientific experiments. I conclude with a discussion of the future of computational scientific discovery.

Recent work on physical quantities has focused on a debate over absolutism vs. comparativism about quantities. In this talk I will be interested in whether this debate can be decided by arguments from physics. I will look at several case studies from the physical sciences, some of which have been invoked to make a case for comparativism, while others seem suitable to support absolutism. I argue that none of the case studies succeeds as an argument in favour of comparativism. In the final part of the talk I turn to the question whether any of the case studies makes a decisive case for absolutism.

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…