## 2013-2014

10 May 2014, 3pm, LPS seminar room

**Tomasz Bigaj (Warsaw) on “Weak discernibility for quanta: why settle for less?”**

Abstract: My talk will consist of two (connected) parts. In the first part I will share with the audience the frustrations resulting from my struggle to understand the multitude of weakly discerning quantum-mechanical relations that have recently been proposed in the literature (Muller & Saunders 2008, Muller & Seevinck 2009, Caulton 2013, Huggett & Norton 2014). On the basis of my understanding of the philosophical motivations behind the whole weak discernibility program, I will attempt to argue that virtually all the proposed methods of discerning quantum particles are fatally flawed. In the face of this setback I will subsequently try to reverse the fortunes of discernibility by arguing that even absolute discernibility of fermions and bosons of the same type is sometimes attainable if we do it right, i.e. using properly symmetrized projection operators.

Previous acquaintance with the papers cited in the abstract can be helpful but is not necessary. The second part of the talk will be loosely based on the unpublished manuscript “Quantum particles, individual properties, and discernibility”.

13 April 2014, 3pm, LPS seminar room

**Eleanor Knox (Kings College, London) on “Spacetime Structuralism or Spacetime Functionalism?”**

Abstract: I examine some currently popular articulations of ontic structural realism with respect to spacetime points, and find them lacking. Instead, I propose functionalism about spacetime itself (with at most derivative consequences for its points). This has much in common with structuralist positions, but has the virtue of usefully applying to emergent spacetimes.

Please read Eleanor’s preprint in advance of the meeting.

22 February 2014, 3pm, LPS seminar room

**Holger Lyre (Magdeburg) on “Berry phase and quantum structural realism”**

Abstract: The purpose of the talk is to analyze the phenomenon of the Berry phase, to spell out its relevance for the quantum state space structure, and to argue for a realist position about this structure. While common wisdom tells us that the quantum state space is the projective Hilbert space, the appropriate structure rich enough to account for the Berry phase turns out to be a U(1) principal bundle over that projective space. Call this the quantum bundle. The Berry phase is the only known instance of a geometric quantum holonomy that, in the absence of any further causal mechanism to bring about this phenomenon, is directly rooted in the curvature of the quantum bundle. This motivates the claim that Berry’s geometric quantum holonomy supports ontic structural realism.

Please read Holger’s preprint in advance of the meeting.

11 January 2014, 3pm, LPS seminar room

**David Wallace (Oxford) on “Thoughts on the Gauge Principle”**

Abstract: Gauge symmetry occupies a paradoxical position in contemporary physics. How can one and the same thing be (a) the third pillar of relativistic quantum field theory, alongside special relativity and quantum mechanics, and (b) a mere descriptive redundancy, indicating that we have overdescribed the theory’s degrees of freedom? Working mostly in classical field theory but motivated by its application in quantum field theory, I will attempt to get some clarity on what we are really saying about a theory conceptually and metaphysically when we say that it has gauge symmetry. Along the way I hope to shed some light on the vexed question of in what sense general relativity is also a gauge theory.

There is no reading for this meeting.

7 December 2013, 3pm, LPS seminar room

** Foad Dizadji-Bahmani (CSU Los Angeles) on “A New Model of Intertheoretic Reduction”**

Preamble/Motivation: Intertheoretic reduction is a perennial theme in philosophy of science; it is a topic that has been present since the very beginning of analytic philosophy of science. There is a striking variety of reductive claims. Some claim that the very modus operandum of science is reductive, others that the history of science is replete with reductions, others still that the putative exemplars of reduction in science are not reductions after all, and yet others that intertheoretic reduction is not possible. Tied up with intertheoretic reduction are the notions of ontological reduction and reductionism. Yet, before one can consider whether or not reductions are ubiquitous, numerous, few, or impossible; whether science aims at reduction; whether all of science does reduce to physics; and so forth, one must first settle what it is for one theory to reduce to another.

Abstract: In this paper I develop and defend a new model of intertheoretic reduction. First, I advocate a particular method for developing some such model, which is a constitutive approach in contradistinction to one based on reflective equilibrium. Second, using this method, I take the relation between the Boyles-Charles law of classical thermodynamics and the so-called kinetic theory of gases to be constitutive of reduction. Third, I discuss how this model compares to Nagel’s well-known model, and, in particular, how my model avoids many of the well-known problems with Nagel’s. Fourth, I apply the model to the relation between a) the classical 2nd Law of Thermodynamics and Boltzmannian statistical mechanics, and b) the classical 2nd Law of Thermodynamics and what in previous work I have called the Aharonov approach to quantum statistical mechanics.

This is no reading for this meeting.

2 November 2013, 4:15pm, LPS seminar room

**Kerry McKenzie (Western) on “Prescriptions on Priority”**

Abstract: In my recent work ‘Priority and Particle Physics’, I suggested that ontic structural realists could use resources gleaned from analytic metaphysics to sharpen up their fundamentality claims — most obviously that concerning the supposed priority of structures over objects. In this talk I want to reconsider that strategy, and investigate whether the fundamentality metaphysics needed for philosophy of physics can in fact be done ‘in house’. After walking us through some priority claims made by philosophers of physics, I will argue that our handling of priority could definitely use some conceptual clear-up. But I’ll also argue that the task of better articulating the concept will be largely continuous with other, antecedently familiar issues in the philosophy of science. While this seems to prise fundamentality questions a little way out of the armchair, what is noteworthy — and dare I say disappointing?! — is that the conception of ontological priority we thereby arrive at looks a lot like that defended in contemporary analytic metaphysics. The significance of this for the much-discussed antagonism between the two fields is a question I’ll leave on the table.

Readings: Although there isn’t a paper associated with the talk, Kerry suggests reading her earlier paper for background.