Warsaw Spacetime Colloquium: Richard Dawid (21 January on Zoom)

On Friday, 21 January, Richard Dawid (Stockholm University) will give a talk titled “Final but Incomplete – What String Theory May Suggest for 21st Century Physics” (abstract below).

The meeting will be online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT

String theory has not come close to a complete formulation after half a century of intense research. On the other hand, a number of features of the theory suggest that the theory, once completed, may be a final theory. It is argued in this talk that those two conspicuous characteristics of string physics are related to each other. The property that links them together is the fact that string theory has no free parameters at a fundamental level. The talk will discuss what finality could mean under the given circumstances and will look at possible implications of this situation for the long term prospects of theory building in fundamental physics.

Warsaw Spacetime Colloquium: Elise Crull (7 January on Zoom)

On Friday, 7 January, Elise Crull (City University of New York) will give a talk titled “You’re a Good Man, Harvey Brown: Quantum Rods & Clocks from Decoherence” (abstract below).

The meeting will be online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT

Harvey Brown’s 2005 book Physical Relativity calls for the development of a constructive-theoretic (as opposed to principle-theoretic) interpretation of relativity: in short, for a quantum-dynamical description of rods and clocks. Significant issues, however, stand in the way of this project. For one, such an interpretation of GR will require carrying over the Strong Equivalence Principle from SR, and this is not trivial. For another, a quantum-dynamical GR is clearly in tension with the fact that the fields in Einstein’s field equations are classical.

Warsaw Spacetime Colloquium: Alastair Wilson (17 December on Zoom)

On Friday, 17 December, Alastair Wilson (University of Birmingham) will give a talk titled “Fundamentality and Levels in Everettian Quantum Mechanics” (abstract below).

The meeting will take place online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT

Distinctions in fundamentality between different levels of description are central to the viability of contemporary decoherence-based Everettian quantum mechanics (EQM). This approach to quantum theory characteristically combines a determinate fundamental reality (one universal wavefunction) with an indeterminate emergent reality (multiple decoherent worlds). In this talk I explore how the Everettian appeal to fundamentality and emergence can be understood within existing metaphysical frameworks, identify grounding and concept fundamentality as promising theoretical tools, and use them to characterize a system of explanatory levels (with associated laws of nature) for EQM. This Everettian level structure encompasses and extends the ‘classical’ levels structure. The ‘classical’ levels of physics, chemistry, biology, etc. are recovered, but they are emergent in character and potentially variable across Everett worlds. EQM invokes an additional fundamental level, not present in the classical levels picture, and a novel potential role for self-location in interlevel metaphysics. When given a modal realist interpretation, EQM also makes trouble for supervenience-based approaches to levels.

Warsaw Spacetime Colloquium: David Albert (3 December on Zoom)

On Friday, 3 December, David Albert (Columbia University) will give a talk titled “Physical Laws and Physical Things” (abstract below).

The meeting will take place online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT

I will consider several strategies for absorbing unwanted pieces of concrete physical ontology (for example: absolute/substantival Newtonian space, Maxwellian Electromagnetic fields, and especially and particularly quantum-mechanical wave-functions) into the metaphysical category of Laws. I will argue that these strategies work well for the case of Newtonian absolute space – but that they work poorly for the case of quantum-mechanical wave-functions.

Warsaw Spacetime Colloquium: Jeremy Butterfield & Henrique Gomes (19 November on Zoom)

On Friday, 19 November, Jeremy Butterfield & Henrique Gomes (University of Cambridge) will give a talk titled “Assessing the Hole Argument” (abstract below).

The meeting will take place online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT

We assess the hole argument in general relativity, and the related topics of the definitions of symmetries and determinism. We begin by rejecting the claim made in some recent literature that the sheer mathematics of the theory makes it mandatory to identify spacetime points “across possible worlds” by dragging along by the isomorphism. We agree that the mathematics is indifferent to the identity of points, and that in many contexts, drag-along is appropriate. But we argue that general relativity, and indeed other spacetime theories, use other means of “trans-world identification”, which we will call threading. Besides, they need to use threading, on pain of trivialising important constructions: even elementary ones like the Lie derivative.

Warsaw Spacetime Colloquium: Robert DiSalle (5 November on Zoom)

On Friday, 5 November, Robert DiSalle (Western University) will give a talk titled “On the epistemological foundations of space-time geometry” (abstract below).

The meeting will take place online on Zoom (17:00-19:00 CET). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT
According to Einstein, what was central to the motivating arguments for the general theory of relativity included not only the familiar arguments about generalizing the relativity of motion, but also the more complicated argument about the empirical content of space-time geometry. On this matter, Einstein’s views, broadly speaking, reflected the influence and insight of Poincaré and Hilbert regarding the empirical interpretation of formal structures. More specifically, however, Einstein offered a reductive analysis of the empirical foundation of geometry, that is, the argument reducing geometrical measurements to observations of “point-coincidences.” This reductive argument in turn inspired logical empiricist conceptions of the empirical content of formal theories. This paper draws a sharp contrast between such conception and the way in which the theory actually determines its characteristic theoretical magnitudes, such as the curvature of space-time. It suggests that the reductive analysis ultimately obscures the empirical significance of general relativity as a novel theory of gravity and space-time, and the nature of the evidentiary basis for this dramatic conceptual shift. I outline an alternative account of how general relativity connects with spatial and temporal measurement, based in the history of the epistemology of geometry, by extending historical analyses of spatial measurement, and of the empirical character of non-Euclidean geometry, to the analysis of curved space-time. This account suggests, more generally, an account of scientific representation, and of the links between empirical descriptions and mathematical structures, that avoids the characteristic difficulties of standard recent approaches.

Warsaw Spacetime Colloquium: Gordon Belot (22 October on Zoom)

On Friday, 22 October, Gordon Belot (University of Michigan) will give a talk titled “The Mach-Einstein Principle of 1917-1918” (abstract below).

The meeting will take place online on Zoom (17:00-19:00 CEST). If you have not registered yet, you can do so here.

You can address any inquiry to antonio.vassallo@pw.edu.pl.

ABSTRACT
In 1917 and 1918 Einstein was working on relativistic cosmology and on promoting and explaining general relativity in correspondence. During this period, the thesis that the spacetime metric should be determined by the distribution of matter played an important role in his thought. This talk is concerned with interpreting this thesis and with investigating its status in general relativity.

Warsaw Spacetime Colloquium 2021/2022 (online)

The Philosophy of Physics Group at the Warsaw University of Technology is happy to announce the Warsaw Spacetime Colloquium 2021-2022.

The Colloquium focuses on the foundations of spacetime physics broadly construed and will be held fortnightly on Zoom.

The program for the winter semester is the following:

22 October (17:00-19:00 CEST) – Gordon Belot (University of Michigan) – “The Mach-Einstein Principle of 1917-1918.”

5 November (17:00-19:00 CET) – Robert DiSalle (Western University) – TBA

19 November (17:00-19:00 CET) – Jeremy Butterfield & Henrique Gomes (University of Cambridge) – “Assessing the Hole Argument.”

3 December (17:00-19:00 CET) – David Albert (Columbia University) – TBA

17 December (17:00-19:00 CET) – Alastair Wilson (University of Birmingham) – “Spatiotemporal Contingency.”

7 January (17:00-19:00 CET) – Elise Crull (City University New York) – TBA

21 January (17:00-19:00 CEST) – Richard Dawid (Stockholm University) – “Final but Incomplete: What String Theory May Suggest for 21st Century Physics.”

People interested in attending the Colloquium can register here.

You can address any query to Antonio Vassallo (antonio.vassallo@pw.edu.pl).

Warsaw Spacetime Colloquium: JB Manchak (28 May on Zoom)

On Friday, 28 May, JB Manchak (University of California, Irvine) will give a talk entitled “On the (In?)Stability of Spacetime Inextendibility” (abstract below).

The meeting will take place online on Zoom (17:00-19:00 CEST). If you have not registered yet, you can do so by sending a message to antonio.vassallo@pw.edu.pl.

The Colloquium is organized by the Philosophy of Physics Group at the International Center for Formal Ontology (Faculty of Administration and Social Sciences, Warsaw University of Technology).

The recordings of the previous meetings are available on the ICFO’s YouTube channel.

ABSTRACT
Within the context of general relativity, the “stability” of various spacetime properties has been one important focus of study. It has been argued that “in order to be physically significant, a property of space-time ought to have some form of stability, that is to say, it should be a property of ‘nearby’ space-times” (Hawking and Ellis 1973, p. 197). Questions concerning the stability of spacetime properties are often made precise using the so-called “C^k fine” topologies on any collection of spacetimes with the same underlying manifold. (The property of “stable causality” is often defined using the C^0 fine topology.) Here we review what is known concerning the (in)stability of spacetime properties within this framework. After considering some foundational results concerning causal properties (Hawking 1969; Geroch 1970) and a fascinating drama concerning geodesic (in)completeness (Beem et al. 1996), we focus on the property of spacetime inextendibility about which very little is known. Because inextendibility is defined relative to a background “possibility space” in the form of a standard collection of spacetimes, one can naturally consider variant definitions relative to other collections. (Some formulations of the “cosmic censorship” conjecture rely on such variant definitions of inextendibility.) We find that the stability of “inextendibility” can be highly sensitive to the choice of definition — even when attention is limited to definitions that are relative to “physically reasonable” collections of spacetimes. Indeed, it is not yet clear that there is a physically significant sense in which “inextendibility” is a stable property. We close by drawing attention to some precise open questions which could be explored to clarify the situation.