News

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).

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.

On Friday, 21 May, Baptiste Le Bihan (University of Geneva) will give a talk entitled “Quantum Gravity and Mereology: Not So Simple” (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 program for the summer semester can be found here, while the recordings of the previous meetings are available on the ICFO’s YouTube channel.

ABSTRACT

A number of philosophers have argued in favour of extended simples on the grounds that they are needed by fundamental physics. The arguments typically appeal to theories of quantum gravity. To date, the argument in favour of extended simples has ignored the fact that the very existence of spacetime is put under pressure by quantum gravity. We thus consider the case for extended simples in the context of different views on the existence of spacetime. We show that the case for extended simples based on physics is far more complex than has been previously thought. We present and then map this complexity, in order to present a much more textured picture of the argument for extended simples. (Joint work with Sam Baron)

On Friday, 7 May, Tim Maudlin (New York University) will give a talk entitled “S=kln(B(W)): Boltzmann entropy, the Second Law, and the Architecture of Hell” (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 program for the summer semester can be found here, while the recordings of the previous meetings are available on ICFO’s YouTube channel.

ABSTRACT

The concept of entropy was introduced in the setting of classical thermodynamics, which was agnostic about the microscopic structure of matter. The advent of the atomic theory and the kinetic theory of heat allowed for the same phenomena to be approached from the standpoint of statistical mechanics, a plan originated by Maxwell and Boltzmann. But in order to “translate” or “reduce” classical thermodynamics into the language of statistical mechanics and the kinetic theory, one needs definitions of terms like “temperature” and “pressure” and “entropy” in the language of the microphysics. One famous such definition—commonly ascribe to Boltzmann but actually due to Planck—is S = k ln(W).
I will propose that in a certain explanatory sense this is the wrong definition. And further, that the proper definition sheds light on the reversibility paradoxes and on the role—or lack of one—of the Past Hypothesis in the reduction of classical thermodynamics to statistical mechanics.

On Friday, 23 April, Marco Giovanelli (University of Turin) will give a talk entitled “Special Relativity as a Theory of Principles. Reflections On Einstein’s Distinction between Constructive and Principle Theories” (abstract below).

The meeting will take place online on Zoom (16:00-18:00 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 program for the summer semester can be found here, while the recordings of the previous meetings are available on the ICFO’s YouTube channel.

ABSTRACT
In a 1919 article for the Times of London, Einstein declared relativity theory to be a ‘principle theory,’ like thermodynamics, rather than a ‘constructive theory,’ like the kinetic theory of gases. Over the last decades, Einstein’s distinction has attracted considerable attention. Philosophers have often considered it as Einstein’s fundamental insight into the nature of spacetime, historians as an unoriginal variation on the 19th-century theme. The paper argues that both stances grasp only part of the truth. To understand Einstein’s “theories of theories” properly, one has to disentangle the two threads of its fabric. Einstein introduced at the same time (a) classification of existing theories (b) classification of strategies for finding new theories. Unlike the usual physical theories, special relativity, like thermodynamics, does not directly attempt to construct models of specific physical systems; it provides empirically motivated and mathematically formulated criteria for such theories’ acceptability. After his early success, Einstein became convinced that, in general, instead of directly searching for new theories, it is often more convenient to search for the formal conditions that constraint the number of possible theories. It is indeed using this strategy that Einstein achieved most of his successes. The paper concludes that these two aspects of Einstein’s principles/constructive theories distinction are best framed by resorting to the opposition between ‘byproducts’ and ‘constraints’ (Lange). For Lorentz and Poincaré, the Lorentz-transformations were a by-product of the actual laws governing field and matter, as a feature that they happen to satisfy. Einstein elevated such coincidence into a constraint, a requirement that all possible laws of nature must satisfy. From this perspective, the relativity principle is not a categorical statement about the real but a modal statement about the possible. In this sense, the paper will defend the characterization as special relativity as a “principle theory”—providing general constraints on laws or theories of whatever nature—rather than as constructive theory—either about the material structure of rods and clocks (Brown) or about the geometrical structure of spacetime (Janssen).