Find here our schedule of speakers, which will be updated as new speakers are confirmed. All talks, past and future, are listed here, and links to video of talks are provided.
All talks are zoomed between the centers unless otherwise noted. You are welcome to attend in person, and in general talks will also be livestreamed on our YouTube channel: look under the ‘all activities’ pull-down. Unless noted otherwise, all events are at 11.15am local Chicago time if held at UIC, and at 6pm (for a 6.15pm start) local Geneva time if held in Geneva. At UIC talks are held in room 1430 of University Hall. University of Geneva talks are held in room L208 (Landolt) if they are on Wednesdays, in room PHIL 002 (Philosophes) if they are on Thursdays. Our YouTube channel is at: www.youtube.com/c/BeyondspacetimeNet
or ? We have given a ‘difficulty’ rating for the papers, so that non-specialists can determine whether a talk will be suitable or not. 1/5 is the level of the New York Times science section, or Nova, say; 2/5 the level of the more serious popular science books; 3/5 the level of physics-inclined philosophy of science; 4/5 the level of general philosophy of physics; and 5/5 indicates a physics, or specialist philosophy of quantum gravity background. Roughly speaking. (Please bear in mind that these are subjective judgements of the speakers.)
• Wednesday, 8 March 2023 (Geneva, 16:15) — Lorenzo Lorenzetti (Bristol): Two forms of functional reductionism in physics
Functional reductionism characterises inter-theoretic reduction as the recovery of the upper-level behaviour described by the reduced theory in terms of the lower-level reducing theory. For instance, finding a statistical mechanical realiser that plys the functional role of thermodynamic entropy allows to establish a reductive link betweehn thermodynamics and statistical mechanics.
My aim is to clarify the meaning of functional reductionism in science, with a focus on physics, to flesh out the details of the view and to define both its place with respect to other approaches to reduction and its connection to ontology. I first review the main available framework for functional reduction, originally developed by David Lewis, that I label Syntactic Functional Reductionism. This approach is tied to the syntactic view of theories, is committed to a logical characterisation of functional roles, and it embedded within Nagelian reductionism. Then, I propose a new framework, called Semantic Functional Recutionism. This novel version of functional reduction adopts a semantic view of theories, spells out functional roles mainly in terms of mathematical roles within the models of theories, and is expressed in terms of the related structuralist approach to reduction.
Reading: http://philsci-archive.pitt.edu/21563/ (draft of the paper)
• Wednesday, 8 March 2023 (Geneva, 17:00–please note the non-standard time) — Claus Kiefer (Cologne): Origin of irreversibility in the universe
I discuss whether the origin of the observed arrows of time can be derived from quantum cosmology. After a general discussion of the problem, I address the concept of entropy in cosmology and give some numerical estimates. I then present a brief introduction into the formalism of quantum gravity that I use in the following analysis. I investigate the possibility whether a natural boundary condition of low initial entropy can be imposed on the quantum gravitational state. A tentative scenario is discussed in which the observed arrows of time originate from this quantum state.
References: C. Kiefer, AVS Quantum Sci. 4 (2022)1, 015607 or arXiv:2111.02137 [gr-qc];
H. D. Zeh, The Physical Basis of the Direction of Time, 5th ed. (Springer, Berlin, 2007).
• Wednesday, 15 March 2023 (Geneva, 16:15) — Erik Curiel (LMU Munich): TBA
• Thursday, 25 May 2023 (Lausanne, 17:00–please note the non-standard time and place) — Sam Baron (Australian Catholic University): Causation and quantum gravity
Approaches to quantum gravity seek to reconcile our two most successful theories at the moment, general relativity and quantum mechanics. In some approaches to quantum gravity, such as causal set theory and causal dynamical triangulation, physicists appeal to causation. But does causation in any philosophically interesting sense have a role to play in quantum gravity? Or are physicists using ‘causation’ differently to how it is used in philosophy? I argue that in at least some cases, the use of causation in quantum gravity corresponds to causation in the usual sense found in philosophy, and so there’s some reason to suppose that causation has a role to play in fundamental physics.
Baron, S. and Le Bihan, B. (forthcoming) Causal Theories of Spacetime. Nous. http://philsci-archive.pitt.edu/21568/
Hitchcock, C. (2007) Three Concepts of Causation. Philosophy Compass, 2(3): 508-516. https://compass.onlinelibrary.wiley.com/doi/full/10.1111/j.1747-9991.2007.00084.x
Loll, R. (2019) Quantum Gravity from Causal Dynamical Triangulations: A Review. https://arxiv.org/abs/1905.08669
Surya, S. (2019) The Causal Set Approach to Quantum Gravity. Living Reviews in Relativity, 22. https://link.springer.com/article/10.1007/s41114-019-0023-1
In terms of technical difficulty, this talk rates 2-3/5 Einsteins.
Past Talks (reverse chronological order)
• Wednesday, 6 April 2022 (UIC 11:15) — Anna Ijjas (NYU): Entropy, Black Holes, and the Early Universe
Emerging from a big bang in which gravity is strongly coupled and quantum fluctuations of stress-energy and spacetime are both large, the natural expectation is that the total entropy should be nearly maximal and equally distributed among both stress-energy and gravitational degrees of freedom. However, the observed entropy distribution on the last scattering surface is puzzlingly different, as Penrose has emphasized. In this talk, I will introduce the cosmological entropy problem and discuss our recent proposal to evade it.
• Wednesday, 16 March 2022 (UIC 11:15) — Flaminia Giacomini (Perimeter): Quantum superposition of massive bodies and the nature of gravity in quantum theory and beyond
Recently, table-top experiments involving massive quantum systems have been proposed to test the interface between quantum theory and gravity. I will first analyse a Gedankenexperiment in which entanglement is generated via gravitational interaction between two quantum systems A and B. I will argue that, within a field-theoretic description of the gravitational field and in a Newtonian regime, it is necessary to include in the description some quantum features of gravity (vacuum fluctuations and emission of quantised radiation) to avoid faster than light signalling. I will then present a no-go theorem, which holds independently of the specific description of gravity and for general non-classical systems A and B, stating that the following statements are incompatible: i) gravity is able to generate entanglement; ii) gravity locally mediates the interaction between the non-classical systems; iii) gravity is classical. Finally, I will comment on the implications of the violation of each condition.
• Wednesday, 8 December 2021 (Geneva, 18:15) — Siska de Baerdemaeker (Stockholm): How not to confirm MOND
Abstract: While Lambda-CDM has emerged as the standard model of cosmology, a small group of physicists defends MOND (Modified Newtonian Gravity) as an alternative view on cosmology. Exponents of MOND have employed a broad, at times explicitly philosophical, conceptual perspective in arguing their case. This paper offers reasons why that MONDian defense has been ineffective. First, we argue that the defense of MOND can best be reconstructed as an instance of meta-empirical theory assessment (MEA). The formal employment of MEA-type reasoning by MONDians is unconvincing, however, because it lacks the epistemic cogency required for successful MEA-type reasoning. In the last part of the paper, we draw some lessons for the debate and for MEA more generally.
This talk is based on joint work with Richard Dawid.
• Wednesday, 1st December 2021 at UIC (11.15am Chicago) — Feraz Azhar (Notre Dame): Effective field theories as a novel probe of fine-tuning of cosmic inflation
Abstract: The leading account of several salient observable features of our universe today is provided by the theory of cosmic inflation. But an important and thus far intractable question is whether inflation is generic, or whether it is finely tuned—requiring very precisely specified initial conditions. In this talk I will present work that argues that a recent, model-independent characterization of inflation—-that treats inflation as an effective field theory (EFT)—-promises to address this question in a thoroughly modern and significantly more comprehensive way than in the existing literature. Along the way, I will highlight recent work that addresses the initial conditions problem within the context of a dynamical systems analysis of a specific EFT of inflation, and will describe a roadmap for how such work might be extended to realize the promise claimed above.
• Wednesday, 14 April 2021 — Craig Callender (UCSD) and Eugene Chua (UCSD): No Time for Time from No-Time
Abstract: Programs in quantum gravity often claim that time emerges from fundamentally timeless physics. In the semiclassical time program time arises only after approximations are taken. Here we ask what justifies taking these approximations and show that time seems to sneak in when answering this question. This raises the worry that the approach is either unjustified or circular in deriving time from no–time. Slides
• Wednesday, 10 March 2021 — Fay Dowker (Imperial College London): If Time Had No Beginning
Abstract: Could the universe have had no beginning? I don’t mean, in raising this question, to deny or throw doubt on Big Bang cosmology and the existence in the past of a hot, dense state of Planckian curvature and temperature. But, in that case, how is the question to be interpreted given that—if we accept the standard cosmology— the Lorentzian manifold structure of spacetime breaks down at the Big Bang? Certainly, the continuum concept of time in our cosmological epoch “begins” at the Big Bang. Can we even ask what happened “before” that? The causal set approach to the problem of quantum gravity provides an arena in which to address the question of origins, in which it makes sense to ask what happened before the Big Bang and in which a clear distinction can be made between models of the universe which are “past infinite” and “past finite”. I will describe work with Stav Zalel and Bruno Bento in which we construct a framework for dynamics for causal sets which can result in past infinite universes. Slides
• Wednesday, 3 March 2021 — Christopher Smeenk (Western University): Decoupling from the Initial State?
Abstract: According to inflationary cosmology, the universe passed through a transient phase of exponential expansion that leaves several characteristic imprints in the universe’s post-inflationary state. This paradigm has enjoyed considerable phenomenological success, as a wide range of inflationary models are compatible with observations. The extent to which this success lends credibility to inflation has been a subject of ongoing debate. Here I will focus on whether the predictions of inflation are robust to changes in high-energy physics, or to features of the pre-inflationary initial state. The prospect of describing the early universe successfully without resolving the mysteries of quantum gravity has always been one of inflation’s appealing features. I will review arguments that inflation does not decouple from high energy physics in the same sense as other effective field theories in physics. Establishing how inflation can be implemented in a theory of quantum gravity is an ongoing challenge, and doing so is needed to address several long-standing foundational questions. Slides and references
• Wednesday, 24 February 2021 — Lee Smolin (Perimeter Institute): Temporal Naturalism
Abstract: I discuss the progress of a research program called temporal naturalism, whose aim is to reframe naturalism and relationalism based on the hypotheses that time is fundamental, while space is emergent. By the fundamentality of time we mean that all that is real are causal processes that continually make definite facts out of previously indefinite possibilities, thereby producing novel events out of predecessor events. Good be-ables to construct such a theory from are the views of events, which describe what properties an event was endowed with by its predecessor events, such as energy and momentum. Thus there is a single universe made up of partial views of itself.
In a relational setting and with no distance, coordinates, fields, or trajectories to draw from, the dynamics must be formulated in terms of views, and in particular in terms of differences amongst views. The change between the view of an event and its immediate predecessors provides a notion of kinetic energy while potential energy is related to the variety, which is the total diversity of present causally unrelated views. This is enough to derive a version of many body quantum theory; which lives in a space that we show emerges from the solutions of the theory. Thus the program shows promise of reconciling both the problems of quantum foundations and quantum gravity, within a single completion.
The part of the program just described has been developed under the names of energetic causal sets and the causal theory of views. Another key aspect is the view that the laws of physics cannot be fixed, but must evolve, in a way as to explain how the choices the universe has made of the fundamental forces and particles have come about through an evolutionary, dynamical process. If there is time I will discuss three realizations of this idea: cosmological natural selection, the principle of precedence, and the hypothesis that the vacua of quantum fields can learn to navigate a landscape of possible laws, using the same mechanisms that allow a deep neural network to learn.
This work has appeared in six books and a number of papers; key collaborators have included Julian Barbour, Fotini Markopoulou, Stuart Kauffman, Joao Magueijo, Stephon Alexander, Roberto Mangabeira Unger, Jaron Lanier, Marina Cortes, Andrew Liddle and Clelia Verde. Slides
• Wednesday, 17 February 2021 — Francesca Vidotto (Western): Quantum Gravity in Practice
Abstract: I present a recent concrete calculation in Spinfoam Cosmology -the application of the covariant LQG techniques to the cosmos- as an example to discuss a number of conceptual issues that are at the core of quantum gravity and cosmology. These include: What are the observables when localization does not rely on background space and time? What are the degrees of freedom? What is the role of quantum fluctuations of spacetime? What’s the interplay between the Planck scale and the cosmological scale? How should we think about time in this picture? Slides
• Wednesday, 10 February 2021 — Christian Wüthrich (Geneva): Laws Beyond Spacetime
Abstract: Quantum gravity’s suggestion that spacetime may be emergent and so only exist contingently would force a radical reconception of extant analyses of laws of nature. Humeanism presupposes a spatiotemporal mosaic of particular matters of fact on which laws supervene. I will show how the Humean supervenience basis of non-modal facts can be reconceived, avoiding a reliance on fundamental spacetime. However, it is unclear that naturalistic forms of Humeanism can maintain their commitment to there being no necessary connections among distinct entities. This talk is based on a joint project with Vincent Lam. Slides
• Wednesday, 3 February 2021 — Nick Huggett (UIC): Laws for Nowhere
Abstract: The standard concept of law is, I suggest, significantly spatiotemporal, posing the question of how there can be laws in non-spatiotemporal theories, and most pointedly how laws could hold in non-spatiotemporal regions of spacetime. I describe a couple of quantum gravity models of the Big Bang (in string theory and group field theory), in a provisional attempt to demonstrate how such questions might arise. Slides
• Wednesday, 9 December 2020 over Zoom at 17:15 UTC — Nora Boyd (Siena College): Observation and Intervention are Irrelevant to Empirical Science
Abstract: It is tempting to define empirical science as investigation of the natural world via the methods of observation and targeted intervention in controlled experiments. This would leave much of astronomy, astrophysics, and cosmology in the lurch since research in those fields often focuses on faraway targets that we cannot hope to observe directly much less manipulate. I will argue that, in general, observation and intervention are actually irrelevant to the empirical nature of scientific evidence, and hence for its epistemic utility in learning about nature. Instead, what matters is that the evidence derives from a causal chain that has one end anchored in the worldly target of interest. This view allows us to ask more interesting questions about the epistemology and methodology of space sciences than the traditional approach. I illustrate the fruitfulness of this view by applying it to cases that are otherwise particularly puzzling: a fascinating example of laboratory astrophysics from the National Ignition Facility, the highly processed images of M87*’s accretion disk from the Event Horizon Telescope, and the prospects for empirical constraints on multiverse hypotheses.
• Wednesday, 25 November 2020 over Zoom at 17:15 UTC — Mike D Schneider (Pittsburgh): Trans-Planckian Philosophy of Cosmology
Abstract: I provide some philosophical groundwork for the recently proposed ‘trans-Planckian censorship’ conjecture in theoretical physics. In particular, I argue that early universe cosmology is, at least as we usually understand it, autonomous with regards to quantum gravity, the high energy physics that governs the Planck regime in our universe. Trans-Planckian censorship is then seen as a means of rendering this autonomy a novel empirical constraint within contemporary quantum gravity research.
• Wednesday, 11 November 2020 over Zoom at 17:15 UTC — Robert Brandenberger (McGill): Is inflationary cosmology consistent with fundamental physics?
Abstract: The inflationary scenario has become the paradigm of early universe cosmology. However, recently challenges have been raised as to whether the scenario can be compatible with fundamental physics. I will review the inflationary scenario, introduce the challenges (Swampland Criteria and Trans-Planckian Censorship Conjecture (TCC)), and show that there are alternatives to inflation which are in agreement with current observations, and also satisfy both the swampland criteria and the TCC.
• Wednesday 6 May 2020 at UIC at 09:30 (14:30 UTC) – Andrew Geraci (Northwestern): Searching for “Fifth-forces”, Dark Matter, and Quantum Gravity in the Lab
Abstract: We normally think of large accelerators and massive detectors when we consider the frontiers of elementary particle physics, pushing to understand the universe at higher and higher energy scales. However, several tabletop low-energy experiments are positioned to discover a wide range of new physics beyond the Standard model of particle physics, where feeble interactions require precision measurements rather than high energies. In high vacuum, optically-levitated dielectric nanospheres achieve excellent decoupling from their environment, making force sensing at the zeptonewton level (10-21 N) achievable. In this talk I will describe our progress towards using these sensors for tests of the Newtonian gravitational inverse square law at micron length scales. Optically levitated dielectric objects and show promise for a variety of other applications, including searches for gravitational waves and Dark Matter. Cooling these objects into the quantum regime of their motion paves the way for tests of quantum coherence in macroscopic objects and tests of whether gravity can destroy such coherence. Looking forward, these systems may enable us to examine the role that gravity plays in quantum mechanical entanglement.
• Thursday 30 April 2020 at Geneva at 16:15 (14:15 UTC) – Erik Curiel (LMU Munich): On the mathematical, physical, and conceptual cogency of quantum field theory on curved spacetime
Abstract: Quantum field theory on curved spacetime (QFT-CST) is the framework within which our current theories about quantum effects around black holes are formulated. The results of their study, including most famously the Hawking effect and its infamous spawn the information-loss paradox, have revealed several surprises that threaten to overturn the views of space, time, and matter that general relativity and quantum field theory each on their own suggests. In partiular, they appear to point to a deep and hitherto unsuspected connection among our three most fundamental theories, general relativity, quantum field theory and thermodynamics. As such, work in QFT-CST provides some of the most important, central, and fruitful fields of study in theoretical physics, bringing together workers from a variety of fields such as cosmology, general relativity, quantum field theory, particle physics, fluid dynamics, condensed matter, and quantum gravity, providing bridges that now closely connect disciplines once seen as largely independent. The framework, however, has serious mathematical, physical and conceptual problems. In this talk, I will provide a sketch of the framework and a survey of some of the most important problems it faces.
• Wednesday 16 October 2019 at UIC at 11 am – Fedele Lizzi (Napoli): Pointless Physics
Abstract: I will describe the role of points in modern physics, and in particular in the attempts to built a theory of quantum gravity. Modern theories will require a quantum spacetime, and in it the usual concept of point, as we have used so far, may lose its meaning. In particular I will discuss noncommutative geometry, a branch born to describe the quantum space of velocity and momenta, and how it could be useful in quantum gravity.
• Wednesday 15 May 2019 at Geneva – Patricia Palacios (Salzburg; with Lapo Casetti, University of Florence): Re-defining equilibrium for long-range interacting systems
Abstract: Long-range interacting systems (LRI) are systems in which the interaction potential decays slowly for large inter-particle distance. Typical examples of long-range interactions are the gravitational and Coulomb forces. The philosophical interest for studying these kinds of systems has to do with the fact that they exhibit properties that escape traditional definitions of equilibrium based on stationary probability distributions. How should we define equilibrium for LRI then? In this contribution, we argue that a comparison with ergodicity-breaking phase transitions gives us a qualitative understanding of equilibrium for these kinds of systems in terms of metastable equilibria. As in the case of phase transitions, we contend that in LRI one could account for metastable equilibria by defining the dynamics for finite-time scales. However, in contrast to phase transitions, we show that these metastable states depend on unknown initial conditions and do not correspond to Boltzmannian equilibrium. This negative conclusion provides a possible basis for future scientific research.
• Wednesday 8 May 2019 at Geneva – Giovanni Valente (Politecnico di Milano): Spontaneous symmetry breaking and physical inequivalence: the case of quantum statistical mechanics
Abstract: In this talk I discuss an outstanding issue in philosophy of physics concerning the relation between quantum symmetries and the notion of physical equivalence. Specifically, I deal with a dilemma arising for quantum symmetry breaking that was posed by Baker (2011), who claimed that if two ground states are connected by a symmetry, even when it is broken, they must be physically equivalent. However, I argue that the dilemma is just apparent. In fact, I object to Baker’s conclusion by showing that the two thermodynamical phases of a ferromagnet, which are connected by the so-called flip-flop symmetry, are physically inequivalent, thereby providing a counter-example to his claim.
• Wednesday 17 April 2019 at Geneva – Miklos Redei (London School of Economics): Categorial local quantum physics
Abstract: The talk reviews the basic ideas of the categorial approach to quantum field theory initiated by Brunetti, Fredenhagen and Verch (2003). The key concept in this approach is a covariant functor representing the quantum field. The functor is between the category of physically reasonable spactimes and the category of C* algebras representing observables localized in a given spacetime. The causal independence of spacelike separated quantum systems is implemented in this framework by imposing locality conditions on the covariant functor. In addition to discussing the usual locality conditions, the talk presents a purely categorial notion of subobject independence in a general category. It is argued that specifying the suggested categorial subobject independence concept in terms of the category of operator algebras with operations as morphisms one obtains an independence condition that should be postulated for the covariant functor to hold in order to express physical locality in categorial local quantum field theory.
Reference: Z. Gyenis & M. Redei: “Categorial Subsystem Independence as Morphism Co-possibility”, Communications in Mathematical Physics, vol. 357 (2018) 447–465, https://doi.org/10.1007/s00220-017-2940-8
• Wednesday 13 March 2019 at Geneva – Bryan Roberts (London School of Economics): Time reversal
Abstract: What does it mean to “reverse time”? The idea sounds sci-fi, but plays an essential role in modern physics. This talk begins with an easy-going overview of how physicists understand time reversal, how it’s related to the philosophy of time and its direction, and why all this matters. I then review a competing, seemingly-intuitive philosophical account of time reversal, but which concludes that physicists have been wrong about it for a hundred years. I finally argue that we should resist this competing account, and stick with the physicists on the meaning of time reversal, both from a philosopher’s and from a physicist’s point of view.
Reference: B.W. Roberts, ‘Time reversal’, http://philsci-archive.pitt.edu/15033/.
• Wednesday 27 February 2019 at Geneva – Jos Uffink (Minnesota): Schrödinger and the prehistory of the EPR argument
Abstract: Although Schrödinger only coined the term “entanglement” (Verschränkung) in 1935, he had been worrying about the phenomenon of (what we now call) entanglement for composite systems since 1927. Indeed, he gave up on his original interpretation of the wave function precisely for this reason. At that time, he thought that Born’s statistical interpretation of the wave function did not suffer from the same problem. In November 1931, his unpublished notebooks show that, in response to a lecture in Berlin by Einstein on the photon box experiment, he already developed all essentials of what we now know as the EPR argument, (Einstein, Podolski and Rosen, 1935). I will argue that Schrödinger’s role in the development of this argument have not yet been sufficiently appreciated by historians of physics. Also, I will comment on the differences between Schrödinger’s and Einstein’s views on the conclusions to be drawn from this argument.
• Wednesday 5 December 2018 at Geneva – Laura Felline (Roma 3): Quantum theory is not only about information part I: ontic approaches This talk in cancelled and will be given at a later time TBA.
Abstract: This talk is part of a bigger project, where I assess the claim that Quantum Theory is a theory about information, by examining whether informational approaches have the resources to explain (or explain away) quantum conundrums. In this talk, I focus on approaches where the quantum state is interpreted ontically as information (e.g. Bub’s information-theoretic approach (2016)), and on their explanation of quantum non-local correlations. First of all, I show how a successful explanation of quantum correlations requires a pre-existing solution to the measurement problem. Secondly, I argue that ontic interpretations (contrarily to epistemic) fail to provide a successful solution to the measurement problem. I conclude that informational ontic approaches to quantum theory can’t constitute a full interpretation of Quantum Theory. In terms of technical difficulty, this talk rates 4/5.
• Wednesday 14 November 2018 at UIC – Sebastian de Haro (Amsterdam): On Theoretical Equivalence and Duality
Abstract: Theoretical equivalence and duality are two closely related notions: but their interconnection has so far not been well understood. In this paper I explicate the contribution of a recent schema for duality to discussions of theoretical equivalence and physical equivalence. I argue that duality suggests a construal of theoretical equivalence for the physical sciences. The construal is in terms of the isomorphism of models, as defined by the Schema. I illustrate the construal in various formulations of Maxwell’s electromagnetic theory, and in electric-magnetic duality. In terms of technical difficulty, this talk rates 3/5
• Wednesday 17 October 2018 at UIC – David Wallace (Southern California): Why black hole information loss is paradoxical
Abstract: I distinguish between two versions of the black hole information-loss paradox. The first arises from apparent failure of unitarity on the space- time of a completely evaporating black hole, which appears to be non- globally-hyperbolic; this is the most commonly discussed version of the paradox in the foundational and semi-popular literature, and the case for calling it ‘paradoxical’ is less than compelling. But the second arises from a clash between a fully-statistical-mechanical interpretation of black hole evaporation and the quantum-field-theoretic description used in derivations of the Hawking effect. This version of the paradox arises long before a black hole completely evaporates, seems to be the version that has played a central role in quantum gravity, and is genuinely paradoxical. After explicating the paradox, I discuss the implications of more recent work on AdS/CFT duality and on the ‘Firewall paradox’, and conclude that the paradox is if anything now sharper. The article is written at a (relatively) introductory level and does not assume advanced knowledge of quantum gravity.
• Thursday 4 October 2018 at Geneva – Mauro Dorato (Roma 3): Dynamical versus structural explanations in scientific revolutions
Abstract: By briefly reviewing three well-known scientific revolutions in fundamental physics (the discovery of inertia, of special relativity and of general relativity), I claim that problems that were supposed to be crying for a dynamical explanation in the old paradigm ended up receiving a structural explanation in the new one. This claim is meant to give more substance to Kuhn’s view that revolutions are accompanied by a shift in what needs to be explained, while suggesting at the same time the existence of a pattern that is common to all of the discussed case-studies. It remains to be seen whether also quantum mechanics, in particular entanglement, conforms to this pattern. In terms of technical difficulty, this talk rates 4/5.
Talks in the period 2015-18 were made possible by the Space and Time After Quantum Gravity grant from the John Templeton Foundation
• Wednesday 23 May 2018 at Geneva – Lina Jansson (Nottingham): Is time like space when it comes to explanatory directionality?
Abstract: There is a distinction about predictions and retrodictions in terms of the role that they play in scientific reasoning that has no analogous distinction in spatial terms. For example, predictive derivations sometimes seem explanatory but retrodictive derivations typically do not. This distinction is often captured in causal terms against the background of a fixed temporal order. I will present an alternative way to capture this distinction and consider how it fits with various approaches to the “problem of time”. In terms of technical difficulty, this talk rates 2/5
• Wednesday 9 May 2018 at Geneva – Yuval Dolev (Bar-Ilan University): Physics’ silence on time
Abstract: In this talk I argue that physics is, always was, and probably always will be voiceless with respect to tense and passage, and that, therefore, if, as I believe, tense and passage are the essence of time, physics’ contribution to our understanding of time can only be limited. The argument, in a nutshell, is that if “physics has no possibility of expression for the Now”, to quote Einstein, then it cannot add anything to the study of tense and passage, and specifically, cannot add anything to the debate between deniers and affirmers of the existence or reality of tense and passage. Since relativity theory did not equip physics with a new language with which to speak of tense and passage, I draw the further conclusion that relativity theory has not generated the revolution to our conception of time that is attributed to it. In the last section I discuss the motivations behind the continued but misguided attempts to integrate tense into a relativistic setting, and assess the manners in which relativity theory has nevertheless enhanced, albeit indirectly, our understanding of tense and passage. In terms of technical difficulty, this talk rates 1/5 This talk will not be skyped to UIC.
• Thursday 3 May 2018 at Geneva at 16:15– DOUBLE HEADER!
Niels Martens (RWTH Aachen University/Epistemology of the LHC Research Unit): Dark Matter = Modified Gravity? Scrutinising the spacetime-matter distinction through the modified gravity/dark matter lens
Abstract: When applying the laws of gravity to the luminous matter that we observe around us in the universe, one obtains an evolution of that matter which is not empirically adequate—at the scale of galaxies and galaxy clusters as well as at the cosmological scale. We face a dilemma between two options that seem to be obviously distinct: either the matter sector needs to be complemented with non-luminous (i.e. dark) matter (DM), or the gravity/spacetime sector needs to be modified (MG) (or perhaps a bit of both). In this paper, co-authored with Dennis Lehmkuhl, we investigate what criterion, if any, is supposed to conceptually distinguish DM theories from MG theories. In doing so, we not only draw upon literature on the broader distinction between matter on the one hand and spacetime/gravity/geometry on the other, we also move in the other direction by pointing out the implications of the uncovered ambiguities inherent in the DM/MG dichotomy for this broader distinction. More specifically, we compare Khoury and Berezhiani’s Superfluid Dark Matter with Hossenfelder’s Lagrangian formulation of Verlinde’s emergent gravity. We extract from the literature a family of candidates for being necessary and/or sufficient criteria for an object being (dark) matter, as well as a similar family of criteria that determine whether an object is a (modified) spacetime. Both of the above theories score (almost) maximally with respect to both families of criteria: both theories are as much of a dark matter theory as possible, as well as being (almost) as much of a modified spacetime/gravity theory as possible. This case study is a first sign that the distinction between modified gravity and dark matter theories—and by extension the spacetime-matter dichotomy—is much less clear than usually assumed, even before reaching the regime where quantum gravity reigns. This blurring severely undermines the current animosity between dark matter advocates and modified gravity advocates, as well as the substantivalism-relationalism debate (where both camps agree that spacetime and matter are clearly conceptually distinct). In terms of technical difficulty, this talk rates 4/5(in parts).
Kian Salimkhani (University of Bonn): On pregeometry (joint work with Niels Linnemann)
Abstract: In this talk, I will investigate the extent to which the dynamical approach to spacetime theories is able to overcome geometry. Famously, the dynamical approach is accused by Norton (2008) of failing to completely reduce geometric spatiotemporal features to matter properties: already setting up the matter fields requires some kind of background structure—some sort of pregeometry. The dynamical approach might be able to evade this criticism as it is primarily concerned with explaining the chronogeometric significance of the metric field, not with explaining how geometry per se emerges from matter properties. Brown and Pooley have responded accordingly; Menon (2018) takes this as conceding too much. After all,—as Norton already noted—it is unnatural to stop the project of explaining geometric properties from matter at the level of metric properties; why not continue? More ambitiously, Menon argues that (physical) geometry per se can indeed be seen as derivative of fields within an algebraic reformulation of the standard fields-on-a-manifold representation. I will first argue that a related issue cannot be circumvented in the context of particle physics’ approaches to GR, and its clarification thus is of central importance not just within interpretational debates regarding GR proper. I will then discuss the issue of pregeometry, and finally stress parallels and disanalogies of these considerations to those concerning the manifold structure in GR. In terms of technical difficulty, this talk rates 3/5
• Wednesday 2 May 2018 at Geneva – DOUBLE HEADER!
Sonali Mohapatra (University of Sussex): Non-local effective quantum gravity and gravitational waves
Abstract: In this talk, I will briefly describe the non-local effective field theory approach to quantum gravity and show some of the predictions such as new modes of gravitational waves. I will then describe some of the open questions in quantum gravity and open the discussion on how to move forward to address the same. In terms of technical difficulty, this talk rates 5/5
Vera Matarese (Czech Academy of Sciences): On the tenability of Humeanism in Loop Quantum Gravity
Abstract: In this talk, I will discuss whether the results of loop quantum gravity (LQG) constitute a fatal blow for Humeanism. There is at least a prima facie reason for believing so: while Humeanism regards spatiotemporal relations as fundamental, loop quantum gravity describes the fundamental layer of our reality in terms of spin networks, from which spacetime should allegedly emerge. However, the question should be tackled more carefully, not only because there are several ways of addressing this issue depending on whether we focus on the letter or on the spirit of Humeanism, but also because there are different views on what the LQG ontological picture should look like. In my discussion, after reviewing the Humean doctrine and the most important ontological interpretations of LQG, I will home in on and evaluate some strategies that the Humeans could adopt to defend their doctrine and find all of them wanting. In terms of technical difficulty, this talk rates 2/5
• Wednesday 25 April 2018 at Geneva – Juliusz Doboszewski (Jagiellonian University Cracow and University of Geneva): On ‘physically unreasonable’ spacetimes in quantum gravity
Abstract: Belot (1998) argued that “our interpretative beliefs about electromagnetism are open to revision in light of quantum effects” (i.e. the Aharonov-Bohm effect). I use the examples of AdS/CFT and black-to-white hole quantum tunneling to argue that contemporary approaches to quantum gravity lead to analogous revision of our assessment of certain general relativistic spacetimes. That is, acceptance of these approaches leads to revision of what one takes to be a physically reasonable spacetime. In terms of technical difficulty, this talk rates 3/5
• Thursday 12 April 2018 at Geneva – Rasmus Jaksland (Norwegian University of Science and Technology): Entanglement as the world-making relation
Abstract: Distance, Michael Esfeld (2017) proposes, is the world-making relation that together with matter points comprise the most meagre ontology of the natural world that is coherent and empirically adequate. This paper offers entanglement – as quantified by entanglement entropy – as an alternative world-making relation. Entanglement is interesting in this regard since it is consistent even with non-spatial theories. The paper thereby defends the metaphysical salience of non-spatial theories, which include a number of the prospective theories of quantum gravity. Obviously, an account of distance (space) is the predominant problem of empirical adequacy facing entanglement as a world-making relation. A possible resolution of this problem utilizes insights from the Ryu-Takayanagi formula (a holographic relation between entanglement and spacetime) and Susskind and Maldacena’s related ER=EPR conjecture (a relation between bell pairs and wormholes). Together, I argue, these indicate a metaphysical interchangeability between entanglement and distance. In this light, some final remarks are made about the notion of non-spatial quantum gravity theories drawing also on Susskind’s recent QM=GR conjecture. In terms of technical difficulty, this talk rates 3/5
• Wednesday 28 March 2018 at Geneva – Adam Koberinski (Western): Problems with the cosmological constant problem
Abstract: “The cosmological constant problem is widely viewed as an important barrier and hint to merging quantum field theory and general relativity. It is a barrier insofar as it remains unsolved, and a solution may hint at a fuller theory of quantum gravity. I critically examine the arguments used to pose the cosmological constant problem, and find many of the steps poorly justified. In particular, there is little reason to accept an absolute zero point energy scale in quantum field theory, and standard calculations are badly divergent. It is also unclear exactly how a semiclassical treatment of gravity would include a vacuum energy contribution to the total stress-energy. Large classes of solution strategies are also found to be conceptually wanting. I conclude that one should not accept the cosmological constant problem as a problem that must be solved by a future theory of quantum gravity.” In terms of technical difficulty, this talk rates 3.5/5
• Wednesday 21 March 2018 at Geneva exceptionally at 14:15 and in room B101 in Bastions – Rawad El Skaf (Université Paris 1 Panthéon-Sorbonne/IHPST): The function and limit of Galileo’s falling bodies thought experiment: Absolute weight, specific weight and the medium’s resistance
Abstract: The ongoing epistemological debate on scientific thought experiments (TEs) revolves, in part, around the now famous Galileo’s falling bodies TE and how it could justify its conclusions; for instance by direct a priori access to a law of nature (i.e. Brown) or by being a deductive argument (i.e. Norton). In this paper, I argue that the TE’s function is misrepresented in this a-historical debate as revealing and justifying a law of nature. I retrace the history of this TE and show that it constituted the first step in two general “argumentative strategies”, excogitated by Galileo to defend two different theories of free fall, in 1590’s and then in the 1630’s. I analyse both argumentative strategies and argue that their function was to explore and eliminate potential causal factors: the TE serving to eliminate absolute weight as a causal factor, while the subsequent arguments serving to explore the effect of specific weight, with conflicting conclusions in 1590 and 1638. It will be argued that the TE is best grasped when placed in the context of both argumentative strategies and in analysing Galileo’s restriction, in the TE’s scenario and conclusion, to bodies of the same material or specific weight. In terms of technical difficulty, this talk rates 2/5
• Wednesday 14 March 2018 at UIC – Harvey Brown (Oxford): How Einstein came to employ the action-reaction principle in justifying general relativity (This talk will be skyped to room L107 in Geneva at 17:00 local Geneva time!)
Abstract: Einstein regarded as one of the triumphs of his 1915 theory of gravity — the general theory of relativity — that it vindicated the action–reaction principle, while Newtonian mechanics as well as his 1905 special theory of relativity supposedly violated it. In this paper we examine why Einstein came to emphasise this position several years after the development of general relativity. Several key considerations are relevant to the story: the connection Einstein originally saw between Mach’s analysis of inertia and the principle of general covariance, the waning of Mach’s influence owing to de Sitter’s 1917 results, and Einstein’s detailed correspondence with Moritz Schlick in 1920. The talk is based largely on a joint paper with Dennis Lehmkuhl: ‘Einstein, the reality of space, and the action-reaction principle’, in Einstein, Tagore and the Nature of Reality, Partha Ghose (ed.), Routledge, London and New York, 2016; pp. 9-36. arXiv:1306.4902v1. In terms of technical difficulty, this talk rates 3/5
• Thursday 8 March 2018 at Geneva at 16:15 – Valeriya Chasova (Université catholique de Louvain): Empirical status of theoretical symmetries in spacetime theories
Abstract: Theoretical symmetries usually discussed in physics are theoretical transformations which leave invariant a Lagrangian or equations of motions, and hence preserve predictions as well. Such symmetries are often interpreted as redescriptions of the same physical content, or at best are taken to account for points of view of different observers. Recently two new contexts were brought into discussion of the ontology of theoretical symmetries. One concerns a correspondence between a theoretical symmetry and an empirical symmetry. In this case the theoretical symmetry is said to have direct empirical status (DES). Another concerns a correspondence between a theoretical symmetry and conservation laws. In this case the theoretical symmetry is said to have indirect empirical status (IES). In my presentation I will discuss whether symmetries of special and general relativity have DES and IES, what this could tell us about their ontology and why quantum gravity can throw a new light on these topics. In terms of technical difficulty, this talk rates 3/5
[DES] Greaves H., and D. Wallace, “Empirical Consequences of Symmetries”, British Journal for the Philosophy of Science, 65, 2014, pp. 59-89.
[IES] Brading K., “Which Symmetry? Noether, Weyl, and Conservation of Electric Charge”, Studies in History and Philosophy of Modern Physics, 33, 2002, pp. 3-22.
• Wednesday 7 March 2018 at UIC – Erik Curiel (LMU/Harvard): Two Paths to the Einstein Field Equation from Horizon Thermodynamics
Abstract: There are today two major research programs that attempt to derive
general relativity—the Einstein field equation—from the thermodynamical properties of causal horizons, that based on the work of Jacobson and that on the work of Padmanabhan, both inspired by and relying on the framework of black-hole thermodynamics. Each has had tantalizing, and similar, successes. It does not seem to be widely recognized in the literature, however, that there are deep differences between the two, both in mathematical form and in conceptual foundation. In this talk, I compare the two with the particular aim of teasing out what exactly each takes to be the thermodynamical properties of horizons. The hope is that the differences between the two, and how they arrive at their common goal, may shed light on different ways one may conceive of “purely gravitational” phenomena as being thermodynamical in character, and what it may even mean in the first place to impute thermodynamical characteristics to purely gravitational systems. I also discuss technical and conceptual problems with the approaches, whose resolutions—or even just their sustained attempt—would provide great insight on all these issues as well. In terms of technical difficulty, this talk rates 4/5(in parts).
• Wednesday 28 February 2018 at Geneva – Lucy James (Bristol): What does fundamentality mean and what is its relevance for quantum gravity?
Abstract: I begin with giving some motivation for thinking of fundamentality as being relative or comparative, rather than absolute, in philosophy, with particular emphasis on the philosophy of physics. This results in a fundamentality relation which has the logical structure of a strict partial order. I briefly discuss this logical structure and then go on to explain how it applies to some specific cases where the idea of fundamentality is used in the literature. The overall aim is to establish when this relation holds, what its relata are, and which direction the relation points in between a given pair of relata. To this end, I distinguish two categories of relata: theories and things. I also categorise the relation into an epistemic and a formal or semantic fundamentality relation, which do not always agree about which direction to point when holding between the same pair of relata. I present further problems with attempting to define an overarching metaphysical fundamentality relation before finally giving some positive suggestions for how all of this bears on the quantum gravity problem. In terms of technical difficulty, this talk rates 2/5
• Wednesday 20 December 2017 at Geneva – Vincent Lam (Geneva): Perspectives from general relativity and quantum gravity on laws of nature and causation
Attention: This talk will exceptionally be in room L208 (Landolt, second floor).
Abstract: This talk aims to update and enrich the two main families of metaphysical conceptions—reductive and non-reductive ones—about laws of nature and causation with insights from fundamental spacetime and gravitational physics. One of the crucial implications of the dynamical nature of general relativistic spacetime is that the global spacetime topology can be non-trivial in a way that may be at odds with the temporal (and ‘production’) aspects of non-reductive accounts. We will discuss the status of the global topological constraints that may be imposed on the spacetime structure within the reductive and non-reductive conceptions about laws and causation. Furthermore, we will specifically discuss how the non-linear and elliptic (constrained) structure of general relativity raises difficulties in evaluating counterfactuals in the initial value formulation of the theory. We will conclude with considerations on how to generalize the standard conceptions about laws and causation to the quantum gravity context where spacetime may not be fundamental in some sense. In terms of technical difficulty, this talk mostly rates 1/5 (with a few peaks)
• Wednesday 13 December 2017 at Geneva – Karen Crowther (Geneva): When do we stop digging? Necessary conditions on a fundamental theory
Abstract: In seeking an answer to the question of what it means for a theory to be fundamental, it is enlightening to ask why the current best theories of physics are not generally believed to be fundamental. This reveals a set of conditions that a theory of physics must satisfy in order to be considered fundamental (although it is a further question whether a theory’s satisfaction of these necessary conditions is sufficient for it to be considered fundamental). Physics aspires to describe ever deeper levels of reality, which may be without end. Ultimately, at any stage we may not be able to tell whether we’ve reached rock bottom, or even if there is a base level–nevertheless, I aim here to draft a checklist to help us identify when to stop digging, in the case where we may have reached a candidate for a final theory. I begin by outlining some of the different conceptions of fundamentality associated with modern physics, before explaining why neither our current best theory of matter and forces (the standard model of particle physics), nor our current best theory of spacetime (general relativity), are generally considered fundamental. Following this, I present the necessary conditions that physicists apparently place on a fundamental theory, and I explore what these tell us about the nature of fundamentality. In terms of technical difficulty, this talk rates 1/5
• Wednesday 15 November 2017 at UIC – Laurent Freidel (Perimeter): The Geometry of Relative Locality
Abstract: In this talk I will describe the fundamental tension that forbids us in my view to reconcile gravity with the quantum. I will explain how this tension forces us to profoundly revise the concept of locality and that this can be done by letting go of the hypothesis of Absolute locality. I will formulate what relaxing this hypothesis means and will describe our attempts to flesh out the concept of relative locality. I will also exemplify what relative locality is into specific examples. In particular, we will show how these ideas allows us to natural interpret geometrically the T-duality symmetry of string theory. This symmetry will be seen as relativistic change of frame in a modular space, a notion of space that replaces Minkowski for quantum geometry. I will also show how the geometry of relative locality is intimately linked with generalized geometry and the geometry of quantum mechanics via a natural structure on phase space called Born geometry. Finally, and if time permits, I will comment how relative locality can shade a bright new light on the problem of unification. This talks involves several new important concepts: relative locality, generalized geometry, modular space, Born geometry. I will try to present them in a non technical manner as much as possible. In terms of technical difficulty, this talk rates 4/5
• Wednesday 18 October 2017 at UIC – David Wallace (University of Southern California): The Case for Black Hole Thermodynamics
Abstract: I give a fairly systematic and thorough presentation of the case for regarding black holes as thermodynamic systems in the fullest sense (contra recent work by Dougherty and Callender), with particular attention to (i) the availability in classical black hole thermodynamics of a well-defined notion of adiabatic intervention; (ii) the power of the membrane paradigm to make black hole thermodynamics precise and to extend it to local-equilibrium contexts; (iii) the central role of Hawking radiation in permitting black holes to be in thermal contact with one another; (iv) the wide range of routes by which Hawking radiation can be derived and its back-reaction on the black hole calculated; (v) the interpretation of Hawking radiation close to the black hole as a gravitationally bound thermal atmosphere. In terms of technical difficulty, this talk rates 4/5
• Wednesday 27 September 2017 at Geneva – Alexei Grinbaum (CEA-Saclay/LARSIM): How device-independent approaches change the meaning of physical theory
Abstract: Dirac sought an interpretation of mathematical formalism in terms of physical entities and Einstein insisted that physics should describe “the real states of the real systems”. While Bell inequalities put into question the reality of states, modern device-independent approaches do away with the idea of entities: physical theory may contain no physical systems. Focusing on the correlations between operationally defined inputs and outputs, device-independent methods promote a view more distant from the conventional one than Einstein’s `principle theories’ were from `constructive theories’. On the examples of indefinite causal orders and almost quantum correlations, we ask a puzzling question: if physical theory is not about systems, then what is it about? Device-independent models suggest that physical theory can be `about’ languages. This answer indicates a direction for moving beyond quantum theory. In terms of technical difficulty, this talk rates 4/5
• Wednesday 31 May 2017 at UIC – Nic Teh (Notre Dame): Newton-Cartan theory and Emergent Newtonian Gravitation
Abstract: In recent work on the philosophy of Newtonian gravitation, there has been much discussion of whether the theory’s “spacetime geometry” is best conceived of as Newton-Cartan geometry, on the one hand, or Maxwellian geometry, on the other hand. Roughly speaking, there have been two approaches to understanding this question: one starts from the idea of “relations between observers”, and the other begins from the standard differential geometric architecture of Newton-Cartan theory and the Trautman Recovery Theorem. In this talk, I will explain how the two approaches can be reconciled, thereby yielding “emergent Newtonian gravitation” as a gauge-fixing of Newton-Cartan theory. In terms of technical difficulty, this talk rates 4/5
• Wednesday 24 May 2017 at Geneva – Samuel Fletcher (Minnesota): Reduction, emergence, and direct limits
Abstract: Most discussions of spacetime emergence and the “physical salience” of the structures employed in theories of quantum gravity have understood these terms informally. Applying some new formal definitions based on “similarity structure” on models of theories, I show how to make more precise the sense in which a physical continuum of events could be emergent, and to connect the discussion of physical salience with a precise definition of intertheoretic reduction. As a test example, I consider claims about the emergence of the continuum of relativistic spacetime from direct limits of causal set histories, showing how their justification, though presently incomplete, could be completed. Time permitting, I will comment on the relation between this approach and causal set theory’s hauptvermutung. In terms of technical difficulty, this talk rates 4/5
• Wednesday 10 May 2017 at Geneva – Karim Thébault (Bristol): Cosmic singularity resolution via quantum evolution
Abstract: We offer a new proposal for singularity resolution in quantum cosmology based upon quantum evolution. In particular, we advocate a new approach to the quantization of mini-superspace leading to a Schrödinger equation for the universe. For models with a massless scalar field and positive cosmological constant, we show that well-behaved quantum observables can be constructed, that generic solutions to this equation are singularity-free and that specific solutions display novel phenomenology including a cosmic bounce. In terms of technical difficulty, this talk rates 4/5
• Thursday 4 May 2017 at UIC – Michael Miller (Pittsburgh):Three obstacles to the interpretation of quantum field theory
Abstract: In this talk I will consider three obstacles to the interpretation of perturbative quantum field theory. Each of the obstacles takes the form of a class of infinities in the mathematical expression of the theory. I argue that each of the classes of infinities can be circumvented by taking the empirical content of the theory to have precisely defined, but limited, precision. This shows that with relatively mild modifications to widely accepted interpretive practice, we can interpret empirically adequate models of quantum field theory. In terms of technical difficulty, this talk rates 3/5
• Wednesday 3 May 2017 at UIC – Laura Ruetsche (Michigan): Renormalization Group Realism: An Unduly Skeptical Review
Abstract: One strategy by which the realist might respond to the pessimistic meta-induction is divide et impera: distinguish aspects of our best current theories we can reasonably expect to persist in the face of theory change from idle theoretical wheels, and espouse realism about the distinguished aspects. For the strategy to amount to a move (rather than a promise or a bluff), the realist needs a way to pick out the distinguished aspects. Principles of identification invoking structure, causal powers, and explanatorily essential elements have all been proposed. Each exhibits an open-endedness proponents of divide et impera realism regard as resource and its skeptics as a vice. I intend to explicate and assess a much more precise divide et impera strategy suggested by the recent work of philosophers of physics familiar with effective theories and renormalization group techniques. This strategy, which I’ll call Renormalization Group Realism (RGR), has the virtue of directly engaging the gears of our best current physical theories, the perturbative QFTs making up the Standard Model. The RGR strategy opens by acknowledging those theories to be merely effective. That is, they succeed at experimentally accessible low energy scales because they approximate the implications higher-energy physics (at present unknown) holds for phenomena at those scales. The strategy next appeals to renormalization group (RG) considerations to identify features of these effective theories that are robust under variations in the underlying, unknown higher energy physics. The criterion of robustness is “invariance under the RG flow”—understood as a signature of lower energy physics that’s insensitive to the details of physics at higher energy scales. Features invariant under the RG flow are features it is reasonable to expect to persist through future refinements of physics, features apt for a realismresistant to the pessimistic metainduction. While I’ll endorse the appeal to RG considerations as a resource in the project of making sense of QFT’s empirical success, I’ll also question whether the attitude emerging from the RGR strategy is properly understood as a viable realism of the divide et impera variety. In terms of technical difficulty, this talk rates 3/5
• Wednesday 5 April 2017 at Geneva – Tim Palmer (University of Oxford): What physics needs is not a quantum theory of gravity – but rather a gravitational theory of the quantum
Abstract: Deep theoretical problems raised by the existence of the dark universe and by the conceptually problematic nature of black-hole information are making the need to find a satisfactory synthesis of quantum and gravitational physics more and more pressing. But after more than 50 years of intense research, the holy grail of a satisfactory quantum theory of gravity – quantum gravity for short – does not appear to be in sight. Here I want to propose that the reason for this failure is that we are putting the cart before the horse: instead of trying to fit gravity into the framework of quantum field theory, we should instead be trying to fit the experimental predictions of quantum theory into a more realistic causal geometric framework compatible with general relativity. It may be objected that the various quantum no-go theorems (EPR, GHZ, Bell-CHSH, PBR) make such a proposal impossible. I strongly disagree. I will claim, motivated by the beautiful non-computable fractal geometries of chaos theory, that all these no-go theorems can be resolved in favour of realism and local causality by assuming that the universe can be considered a nonlinear deterministic dynamical system evolving precisely on a type of fractal invariant set in its state space (the word “precisely” being described mathematically by the use of the so-called p-adic metric in state space), and by reinterpreting the complex-number Hilbert vectors of quantum theory accordingly. In describing this “invariant set theory” I will be making essential use of the fact that in the laboratory we cannot screen quantum systems from ubiquitous space-time ripples associated e.g. with distant astrophysical events. This lends weight to the notion, suggested in the title above, that gravity may be playing an essential role in ordinary unitary transformations in laboratory quantum physics (never mind the measurement process) in a way which conventional quantum theory simply cannot account for. For details, see https://arxiv.org/abs/1609.08148. In terms of technical difficulty, this talk rates 3/5
• Wednesday 29 March 2017 at UIC – Tiziana Vistarini (Colorado, Boulder): The metaphysics within string physics
Abstract: It is widely held inside the quantum gravity circles that string theory is a background dependent theory and that for this reason any attempt of tracing in the theory any notion of space and time emergence is simply a non starter. In this talk I argue against this view and I present some trains of thought developed in my book supporting the idea that the theory admits a notion of spacetime emergence. Spacetime emergence in string theory is a notion inextricably connected to that of mechanistic explanation. The main thesis of the view I try to pursue in my book is that space and time in string theory are emergent because they are mechanical byproducts of deeper string dynamics. In what sense would space and time be susceptible of mechanical explanation? One may succinctly answer that they are susceptible in the same sense in which things like tables, clocks, cats and people, and so on, are. My thesis articulates basically in two points. First, the idea that string theory physical content is independent from spacetime structure is grounded on my reading of some crucial information built into the local structure of string theory ‘s moduli space. Explaining this crucial point requires me to unpack at least some of the basic tools of deformation theory I used to explore the fine local structure of this space. The lesson about metaphysics I get here is that string theory does not posit any fundamental geometry, rather it only posits some fundamental topological structure, something much weaker than a metrical one. Second, based on these findings, I try to give a description as much complete as possible of how space and time can be thought in terms of mechanical byproducts. This attempt requires a revised formulation, or I may say, an extended definition of what a mechanical explanation is – a proposal that tries to encompass as specific case the traditional one. In terms of technical difficulty, this talk rates 3/5
• Wednesday 22 March 2017 at Geneva – Keizo Matsubara (UIC): Why Lewisian metaphysics does lead to scepticism
Abstract: Some aspects of Lewisian metaphysics are criticised. Lewis’s account — which combines Humean supervenience with modal realism — is found to be problematic and to lead to scepticism regarding our ability to trust scientific predictions. Critique of the kind presented in this text has been levelled against Lewis before. He has responded by arguing that his metaphysical position is not more problematic than other views. Here it is argued that Lewis’s responses are unsatisfactory. Thus serious belief in Lewis’s account is not compatible with trust in predictions made using our best scientific theories. In terms of technical difficulty, this talk rates 1/5
• Wednesday 8 March 2017 at Geneva – Fay Dowker (Imperial College London): Being and Becoming in Quantum Gravity (or The Birth of a Baby is not a Baby)
Abstract: I will describe a dynamical model of a discrete cosmology — called Classical Sequential Growth — that has been proposed as a stepping stone along the way to full quantum gravity. I will present Sorkin’s argument that this model is a counterexample to the claim that relativity means that the future must exist. I will point out that the model contains two different types of physical thing. One is the Past, which is subjective. The other is the Birth Process by which the atoms of spacetime come into being. Both are real in the model and, I will argue, both are needed if the model is to coordinate with our experience. The price that must be paid for this advance, however, is that the model does not provide a “God’s eye view’’ of the universe. In terms of technical difficulty, this talk rates 4.5/5
• Wednesday 1 March 2017 at Geneva – Philipp Berghofer (Graz): Ontic structural realism and quantum field theory: are there intrinsic properties at the most fundamental level of Reality?
Abstract: Ontic structural realism (OSR), in its radical guise, has it that structures are all there is. This implies that there are no objects. Neither the particles your body is made of, nor the chair you are sitting on really exists. To be sure, radical OSRs do not deny that relations have relata, but they interpret these relata in structural terms. It is relations all the way down. Considering the radicality of this eliminativist view, it comes as no surprise that many researchers sympathetic to OSR have opted for a more moderate version of OSR. Moderate OSR: Objects only have relational but no intrinsic properties. Very recently there has emerged a position that seems to be even more moderate. This is the claim that at the most fundamental level of reality there are only relational properties. In this context, Kerry McKenzie has referred to quantum field theory (QFT) in order to argue for this moderate version of OSR. While I approve this focus on QFT, I am puzzled by McKenzie’s focus on elementary particles. What QFT tells us is that the most fundamental entities are fields, not particles. Particles “merely” are excitations of fields. The question, thus, is: Do fields have intrinsic properties? Finally, I shall discuss what this means for spacetime structuralism and what effects research in quantum gravity might have on OSR. In terms of technical difficulty, this talk rates 2/5
• Wednesday 30 November 2016 at Geneva – Tushar Menon (University of Oxford): Desperate spacetimes call for desperate measures: An argument for superspace realism
Abstract: It is widely believed that the endeavour of combining general relativity with quantum field theory will lead to an overhaul of our conception of spacetime. In the first part of this talk, I discuss which of our intuitions about spacetime ought to survive the move to a quantum theory of gravity. Building on the geometric functionalist approach to spacetime championed by Eleanor Knox, I argue for a more general algebraic characterisation of spacetime degrees of freedom that is dynamically informed. In the second part of the talk, I use this characterisation to argue for a spatiotemporal interpretation of superspace, an extension to Minkowski spacetime which incorporates a number of extra dimensions in order to account for transformation properties of bosonic and fermionic fields under supersymmetry. In terms of technical difficulty, this talk rates 5/5
• Wednesday 23 November 2016 at Geneva – David Yates (University of Lisbon): Spacetime functionalism and empirical coherence
Abstract: Quantum gravity research seems to suggest that spacetime is not fundamental, but this in turn threatens the existence of the “local beables”—meters, pointers, dials—we observe to gain evidence for fundamental physical theories. How can a physical theory be justified if there are no local beables in its ontology? Spacetime functionalism promises a conservative truthmaking theory for empirical truths, which explains how it is that statements such as ‘the pointer moved to position 5 on the dial’ come out true even though the fundamental ontology is not straightforwardly spatiotemporal. There are several different functionalist positions available—depending on which concepts we take to be functional, and what roles we take to define them—and it isn’t always clear how they interact. Spacetime functionalists (Knox) argue that the concept of a spacetime is the concept of whatever it is that occupies a certain set of roles within physical theory. Because the concept of spacetime is topic-neutral, even if the fundamental quantum ontology turns out to be very unlike the spacetime of the manifest image, we should not conclude on that basis that there is no spacetime for local beables to occupy. The occupant of the spacetime roles may or may not be fundamental, and it may or may not be recognisable spatiotemporal. This theory shows us how a necessary condition on the truth of empirical statements is consistent with a non-spatiotemporal fundamental ontology, but stops short of a truthmaking theory for such statements. Spacetime occupant-functionalism (Wallace, Ney) and spacetime property-functionalism (Chalmers) offer topic-neutral analyses of our concepts of ordinary objects and spatiotemporal properties respectively, and jointly offer the promise of such a theory. In this talk I argue that property-functionalism fails, and that there is therefore no topic-neutral analysis of our ordinary empirical claims about local beables. I argue further that at least some spatiotemporal property concepts fail to have topic-neutral analyses because they are directly referring concepts that are at least partially transparent with respect to their referents. It follows, I suggest, that either the fundamental quantum ontology is spatiotemporal after all, or local beables inhabit a grounded spacetime. I suggest the latter, and conclude by considering whether a grounded spacetime might also be fundamental, hence ontologically emergent. In terms of technical difficulty, this talk rates 1/5
• Wednesday 16 November 2016 at UIC – Shamik Dasgupta (University of California, Berkeley): Physical Salience and Autonomy: Could Spacetime be an Emergent Phenomenon?
Abstract: There has recently been much interest in the question of whether space could be derivative from some kind of non-spatial structure. But what conditions must be satisfied if the resulting space is to be, to use Tim Maudlin’s phrase, “physically salient”? Some suggest that there is an epistemic constraint to the effect that it must be “fully transparent” or “immediately intelligible” how space emerges out of the non-spatial structure. In particular, David Chalmers develops this constraint in terms of apriori entailment. But is there really an epistemic constraint like this? If so, why? What is it about something being “derivative from” something else that requires this epistemic connection between the two? I will explore an answer to this latter question, thereby defending epistemic constraints like these from some recent objections. In terms of technical difficulty, this talk rates 1/5
• Wednesday 26 October 2016 at Geneva – Elena Castellani (University of Florence): Duality and emergence: the case of weak/strong duality
Abstract: The two notions of duality and emergence seem to be in an intriguing relation: on the one side, they seem to be closely connected, on the other side, they are clearly distinct —- perhaps even mutually exclusive? The key feature, in the case of duality, is the kind of equivalence that is entailed between the two theories (or the two descriptions of the same theory, in case of self-duality). In the case of emergence, the focus is rather on the aspect of novelty that the notion entails, and thus, apparently, on a lack of equivalence between the two theoretical descriptions. The dualities which are of great relevance in field and string theory, however, seem to be related to emergence: in many cases, the dual correspondence seems to give a form of emergence (new particles or new phenomena). How to combine these apparently contrasting features? This talk is directly connected to the preceding talk by Sebastian de Haro discussing the relation between duality and emergence in the case of gauge/gravity duality (Geneva, 14.01.2016). Here, the same issue is discussed in another relevant duality case, that is, weak-strong duality or S-duality (as is usual to call it in the context of string theory) — a duality which has become a basic ingredient in field and string theories especially since the 1990s. In particular, the focus will be on the meaning of the dual correspondence between ‘elementary’ and ‘composite’ particles that this kind of duality apparently implies. At first sight, the correspondence could be interpreted as giving rise to new objects or a new way of looking at the same objects. The question is then how to intend this novelty feature given the symmetric character of the dual correspondence. The general aim is to explore whether and in which sense comparing duality and emergence can be a helpful exercise for the philosophical reflection on their meaning. In terms of technical difficulty, this talk rates 3/5
• Wednesday 19 October 2016 at Geneva – Marko Vojinovic (University of Belgrade): Quantum gravity, metaphysics, spacetime emergence and locality
Abstract: We will present a brief overview of the various approaches to quantum gravity, with the emphasis on the following questions: (1) why quantize gravity, (2) how to quantize gravity, (3) what is spacetime emergence, and (4) the role of metaphysics in all the above. We will also touch upon the foundational issues of diffeomorphism-symmetric quantum mechanics, and the interplay between locality, the measurement problem, the Schrodinger’s cat paradox and quantum cosmology, leading to some open questions at the foundation of both gravity and quantum mechanics. In terms of technical difficulty, this talk rates 4/5
• Wednesday 12 October 2016 at Geneva – Ko Sanders (University of Leipzig): What can (mathematical) categories tell us about space-time?
Abstract: It is widely believed that in quantum theories of gravity, the classical description of space-time as a manifold is no longer viable as a fundamental concept. Instead, space-time emerges as a suitable approximation. In order to understand what is required to explain this emergence, it is necessary to have a good understanding of the classical structure of space-time. In this presentation I will focus on the concept of space-time as it appears in locally covariant quantum field theory (LCQFT), an axiomatic framework for describing quantum field theories in the presence of gravitational background fields. A key aspect of LCQFT is the way in which it formulates locality and general covariance, using the language of category theory. I will argue that the use of category theory gives a precise and explicit statement of how space-time acts as an organizing principle in a systems view of the world. Along the way I will indicate how categories turn physical theories into a kind of models for modal logic, and how the categorical view of space-time shifts the emphasis away from the manifold structure. The latter point suggests that the view of space-time as an organizing principle may persist, even in a quantum theory of gravity, but it may raise new questions. In terms of technical difficulty, this talk rates 3/5
• Wednesday 5 October 2016 at Geneva – Tatyana Shestakova (Southern Federal University, Rostov-on-Don): Could the Copenhagen interpretation be useful for our understanding of Quantum Cosmology?
Abstract: It is generally accepted that the Copenhagen Interpretation is inapplicable to Quantum Cosmology, by contrast with the many worlds interpretation. I shall try to demonstrate that the two basic principles of the Copenhagen interpretation, the principle of integrity and the principle of complementarity, do make sense in Quantum Gravity, since we can judge about quantum gravitational processes in the very early Universe by their vestiges in our macroscopic Universe. I shall present the extended phase space approach to Quantum Gravity and show that it can be interpreted in the spirit of the Everett’s “relative states” formulation, while there is no contradiction between the “relative states” formulation and the mentioned basic principles of the Copenhagen Interpretation. In terms of technical difficulty, this talk rates 4/5
• Wednesday 21 September 2016 at Geneva – Joshua Norton (American University Beirut): Incubating a future metaphysics: quantum gravity
Abstract: In this talk, I will argue that metaphysicians ought to utilize quantum theories of gravity (QG) as incubators for a future metaphysics. In §1, I will argue why this ought to be done. In §2, I will present case studies from the history of science where physical theories have challenged both the dogmatic and speculative metaphysician. In §3, I will present two theories of QG and demonstrate the challenge they pose to certain aspects of our current metaphysics; in particular, how they challenge our understanding of the abstract-concrete distinction. In this section I demonstrate how five different accounts of the distinction each fail to hold under the received interpretations of loop quantum gravity and string theory. The central goal of this talk is to encourage metaphysicians to look to physical theories, especially those involving cosmology such as string theory and loop quantum gravity, when doing metaphysics. In terms of technical difficulty, this talk rates 2/5
• Friday June 17th 2016 at UIC at 3pm – DOUBLE HEADER!
Radin Dardashti (Munich Center for Mathematical Philosophy, and Geneva): Testing Theories, Theory Space and Scientific Practice
Abstract: “Many scientific theories in fundamental physics are lacking empirical support. While in some cases future experiments may allow empirical testing (supersymmetry), this is less obvious in other cases (theories of quantum gravity, cosmic inflation). One possible way of addressing this problem is to analyse whether empirical evidence provides the only means to confirm our theories. In this talk I will present a generalised perspective on theory confirmation, which relies on the concept of theory space. This allows us to extend the notion of theory confirmation to evidence, which is not necessarily made more or less likely by the theory itself. I will discuss the advantages of this more general perspective on scientific theory assessment, discuss some examples and what their normative implications are for the practicing scientist.” In terms of technical difficulty, this talk rates 2/5
Juliusz Doboszewski (Jagiellonian University, and Geneva): Is anti-de Sitter spacetime physically reasonable?
Abstract: “Solutions of classical general relativity are often divided into physically reasonable and physically unreasonable ones. For example, physically reasonable spacetimes are sometimes expected to satisfy some energy condition, be globally hyperbolic, inextendible, hole free, or stable against perturbations. I will discuss (a) how conditions used to draw such a divide apply to anti-de Sitter spacetime, and (b) how violation of some of them should be interpreted in the context of gauge/gravity duality.” In terms of technical difficulty, this talk rates 4/5
• Wednesday May 25th 2016 at UIC – Henrique Gomes (Perimeter Institute): Timeless Quantum Mechanics in Configuration Space
Abstract: “In this talk, I will argue in favor of a ‘transition amplitude’ approach to quantum gravity. For such a position to be internally consistent, not all types of symmetries are allowed. I will describe which ones are and we will see how refoliations become problematic – I will contend that they should only be recovered dynamically (as an on-shell, or effective, symmetry). Given this ‘transition amplitude’ point of view, I will further elaborate on how the allowed symmetries select a unique ‘in state’ for the amplitude. We can thereby use this ‘in state’ to produce a static wavefunction of the Universe, much like some of the interpretations of the Wheeler-DeWitt. Lastly, I will describe how one can extract our usual notion of time from such a fundamentally timeless view, at least semi-classically, through a structure called ‘semi-classical records’. Time allowing (no pun intended), I will further speculate on some recent progress in a relation between renormalization group flow and a notion of instantaneous duration (this part will be pure speculation).”
• Wednesday May 11th 2016 at Geneva – Francesca Vidotto (Radboud University Nijmegen): How classical spacetime emerges in Loop Quantum Gravity
Abstract: “Is space an entity or a net of relations? Is classical spacetime emergent? If it is emergent, what is it emerging from? Is spacetime fundamentally discrete or continuous? Is time an ingredient of the fundamental equations of the world? Is time flowing? These philosophical questions need to find an answer in a concrete realisation of a quantum theory of gravity. I illustrate the basics of Loop Quantum Gravity and the specific answers that each of these (philosophical) questions finds in the context of this (physical) theory. I focus on the notion of spacetime emergence: I argue that classical spacetime emerges from the quanta of spacetime, no differently from the emergence of electromagnetism having photons. This quantum emergence is studied in Loop Quantum Gravity, where there is a notion of classical limit. This limit should not be confused with a thermodynamical limit, that may exist but it is not necessary to recover classical spacetime. These ideas can be illustrated in analogy with the case of electromagnetism.” In terms of technical difficulty, this talk rates 4/5
• Wednesday April 27th 2016 at UIC – Karen Crowther: The Correspondence Principle in Quantum Gravity
Abstract: “The difficulties in discovering a theory of quantum gravity are due not only to its apparently extreme experimental inaccessibility, but the fact that there are no commonly accepted, formally established constraints that define its basic structure and objectives. I critically examine the role of the correspondence principle in quantum gravity, to evaluate its prospects as such a constraint. I find that there is a form of correspondence that serves as an essential heuristic guide in developing the theory, but that another form of correspondence has acquired a status of undue weight. It seems that the stress on deriving general relativity in the low-energy regime is unwise at this stage of theory-development, and possibly altogether.” In terms of technical difficulty, this talk rates 3/5
• Thursday April 14th 2016 – DOUBLE HEADER!
(1) In Geneva, Giuliano Torrengo (Milan): The experience of the passage of time
Abstract: “It is one of our ordinary beliefs that time passes. And it seems trivial to say that we think this to be so because our experiences tell us so. However, the status of the experience of time passing is a non-trivial matter of debate. Representationalists believe that it is a representational feature of the content of our experience — in the naive version of the theory, something like being red or yellow. Reductionists hold that temporal experiences with qualitative characters, such as experiences as of motion or change, are in some sense responsible for the feeling of the passage of time. Deflationists maintain that there is no distinctive phenomenological character of the passage, but only an intuitive grasp of the ordinary belief that time passes. I will defend what I call the Phenomenal Modifier view. Roughly, according to this view, the feeling of the passage of time should be understood as a modifier of the character and content of experience, just as the blurred, or vivid nature of a visual experience can be seen as modifying the way the experience feels to us.” In terms of technical difficulty, this talk rates 1/5
(2) In Chicago, James Read (Oxford): Background Independence and Holography
Abstract: “I introduce the definitions of background independence due to Belot, Pooley, and de Haro et al. I apply these definitions in order to assess whether bulk theories in gauge/gravity dualities are background independent, finding that one’s verdict hinges crucially upon the definition of background independence at play. In addition, I discuss the so-called ‘diffeomorphism anomaly’, which arises in bulk theories in some cases of gauge/gravity duality.” In terms of technical difficulty, this talk rates 4/5
A reply to Read from De Haro is here: http://bit.ly/1XpgbGj
• Wednesday April 13th 2016 at Geneva – Oliver Pooley (Oxford): Relativity and the growing block
Abstract: “I discuss two problems that stand in the way of reconciling relativistic physics and the growing block view of time. The first problem concerns the status of simultaneity and the present. A metaphysics of time that avoids introducing a preferred simultaneity relation can claim to be more thoroughly relativistic than one that does. A B-theoretic ‘block universe’ model of time can clearly be relativistic in this sense. In other work I have argued that a shrinking tree model that embraces relativism (in Kit Fine’s sense) can be appropriately relativistic. I consider a Growing Block view fashioned along similar lines, and relate it to recent claims by some physicists (Sorkin, Dowker) to the effect that Causal Set Theory offers a physically respectable model of the passage of time. The second problem concerns the interpretation of spatiotemporal relations that hold of events within the Growing Block. Many (including some physicists, such as George Ellis) suppose that a global present, and a metaphysically preferred simultaneity relation, are compatible with the letter of relativity. Adopting this view, one might further claim that for a Growing Block model to be relativistic it is merely required that the physics and spacetime structure of the ever growing block satisfies relativistic laws (Earman). However, the natural interpretation of such models leaves the view vulnerable to the Now now” objection. A promising response in the non-relativistic context insists that the (spatio)temporal structure of the ever growing Block is to be reduced to primitive tense (Correia and Rosencrantz). I explore the difficulties faced when seeking to recover relativistic spatiotemporal relations along these lines.” In terms of technical difficulty, this talk rates 3/5
• Wednesday April 6th 2016 at UIC – Dean Rickles (Sydney): Dual theories: ‘Same but different’ or ‘different but same’?
Abstract: “I argue that, underneath the glitz, dual theories are simply examples of theoretically equivalent descriptions of the same underlying physical content: I distinguish them from cases of genuine underdetermination on the grounds that there is no real incompatibility involved between the descriptions. The incompatibility is at the level of purely unphysical structure. I argue that dual pairs are in fact very strongly analogous to gauge-related solutions even for dual pairs that look the most radically distinct, such as AdS/CFT. However, again by analogy with gauge freedom, I conjecture that dualities always point to a more fundamental (intrinsic) description, namely that in which the representational redundancy is eliminated.” In terms of technical difficulty, this talk rates 3.5/5
• Wednesday March 23rd 2016 at Geneva – Jonathan Dorsey (Texas Tech): Defining the Physical
Abstract: “What is it to be physical? While the answer may seem obvious pre-theoretically, the problem is intractable enough to have earned the epithet ‘the body problem’ in contemporary philosophy. An understanding of what it means to be physical is of crucial importance for many reasons, foremost among them the role this understanding must play in the physicalism debate. I review and reject both the traditional definitions of the physical and the more recent ‘physics-based’ definition. In their place, I propose a ‘physics-guided’ definition. This has three advantages over its predecessors. First, it uses physics strategically, as a guide, in developing a definition of the physical, while stopping short of building physics per se into the very definition. Second, it focuses on the explananda in physics, physics’s explanatory targets, rather than the explanantia, the posits introduced to explain those targets. Third, it produces a traditional-style, direct definition of the physical, while also providing criteria for evaluation and for further development.” In terms of technical difficulty, this talk rates 2/5
• Wednesday March 2nd 2016 at UIC – DOUBLE HEADER!
(1) Eddy Keming Chen (Rutgers): Our Fundamental Physical Space and the Quantum Wave Function
(2) Alastair Wilson (Birmingham): Emergent Spacetime: Grounded or Caused?
Abstract: “Metaphysicians typically distinguish sharply between types of dependence relation: causation on the one hand and grounding (also called metaphysical explanation, or metaphysical dependence) on the other. But there is no consensus, nor much direct discussion, of how to draw this distinction between types of dependence. I make a simple demarcation proposal in terms of modal strength, and apply it in an attempt to cast some light on the status of emergent spacetime structure.” In terms of technical difficulty, this talk rates 2/5
• Wednesday February 24th 2016 at UIC – Richard Dawid (Vienna): String Dualities and Empirical Equivalence
Abstract: “String dualities constitute a specific form of empirical equivalence in physics. One may argue that, after a century when empirical equivalence was primarily of interest to philosophy of science, the rise of duality in string physics marks the first time that empirical equivalence takes centre stage in physics itself. The paper will make the case, however, that the philosophical repercussions of string dualities are in fact directly opposed to the way the significance of empirical equivalence was understood throughout most of the 20th century in philosophy of science as well as physics. Comparing the canonical perspective on empirical equivalence with the role played by duality today provides an interesting indicator of the way string physics has altered the physicists’ perspective on physical theory building.” In terms of technical difficulty, this talk rates 3/5
• Thursday January 14th 2016 at Geneva – Sebastian de Haro (Cambridge and Amsterdam): Emergence in Gauge/Gravity Dualities
Abstract: “Recent developments in gauge/gravity dualities suggest that renormalization group flows and the dynamics of spacetime are intimately related. The direction along which the theory’s couplings ‘flow’, typically an energy scale, is reinterpreted as a dimension (spatial or temporal) in which fields can evolve. It is often claimed that space, time, and-or gravity ‘emerge’ from a lower-dimensional theory in this way.
In this talk I will: (i) present a framework for discussing emergence in cases of duality; (ii) assess the claims of emergence in the best studied case of gauge/gravity duality: the AdS/CFT correspondence; (iii) comment on the possibility of carrying these ideas over to a cosmological context, viz. of de Sitter space-time. Regarding (i): after introducing general notions of duality and emergence, I will argue that these two notions preclude one another. Coarse-graining will come to the rescue, suggesting two possible ways in which emergence can take place in the case of dualities (and I will argue that this exhausts the possibilities). Then I will: (ii) introduce holographic RG techniques as used in AdS/CFT. I will then employ the general framework of dualities and emergence to assess in what sense these are cases of emergence. In the last part of the talk, I will: (iii) discuss the conjectured dS/CFT correspondence for cosmological scenario’s. After (a) discussing some of the difficulties for holographic theories of de Sitter spacetime, I will (b) review current progress on two proposals for dS/CFT, and (c) discuss in what sense time can be said to emerge in such scenarios.” In terms of technical difficulty, this talk rates 4/5
• Wednesday December 2nd 2015 at Geneva – Nick Huggett (UIC): What Does it Take to Explain Spacetime?
Abstract: “In earlier work, Chris Wüthrich and I addressed the question of ‘physical salience’ in the explanation of spacetime, raised by Tim Maudlin. In this talk (the result of continuing collaboration) I aim, with examples, to further explicate the role that physical salience plays in the reduction of one physical level to another (using those terms loosely): in short, physical salience is a stronger ontological condition than ‘mere derivability’. (Though our knowledge of physical salience will ultimately rest on the derivation of empirical predictions.) I then turn to the question of whether the demand of physical salience might be satisfied in an explanation of the appearance of spacetime in terms of non-spatiotemporal physics: I will sketch the example of non-commutative geometry in accessible terms.” In terms of technical difficulty, this talk rates 2/5
• Wednesday November 11th 2015 at UIC — Kerry McKenzie (UC San Diego): Against Brute Fundamentalism
Abstract: “The claim that the fundamental is ‘brute and inexplicable’ is recited almost reflexively in philosophy. But this ‘brutalist’ stance toward the fundamental seems to lie in increasing tension with what physicists claim to aspire to. In this talk, I argue that those aspirations of physicists are not only reasonable, but that there is a sense in which they are already realized. In so doing, I hope to show that the idea that everything can be explained need not be tainted with rationalist overtones, but also to underline how qualified any claim of this nature must ultimately be.” In terms of technical difficulty, this talk rates 3/5
• Wednesday October 28th 2015 at Geneva – Daniele Oriti (Albert Einstein Institute, Golm): If space and time are emergent (in quantum gravity), what is cosmology?
Abstract: “I will discuss three main conceptual aspects of current developments on the nature of space and time in quantum gravity. The first is the need to broaden the context of quantum gravity itself from a theory of quantum General Relativity to a theory of the microstructure of spacetime, founded on non-spatiotemporal building blocks. This changes to some extent the nature of the problem, brings in a new set of conceptual and technical tools (most notably, the renormalisation group and ideas from condensed matter theory), and makes room for a full-blown notion of “emergence” for spacetime itself.The second are the various levels of such “spacetime emergence” in quantum gravity, so intended. Each carries new technical issues and opportunities, related for example to the possible phase structure of a quantum gravity system and of the related phase transitions. This deepens the scope of the debate on the nature of spacetime, both philosophically and physically.
The third is a new perspective on cosmology from the quantum gravity point of view, and more specifically in an emergent spacetime scenario. It is based on the notion of geometrogenesis (a phase transition between a geometric and a non-geometric phase) as a physical process in the history of the universe, replacing the classical big bang singularity, and on the interpretation of cosmological dynamics as the hydrodynamic description of the fundamental microscopic quantum dynamics of the building blocks pf spacetime. I will focus on the conceptual aspects, which have a more general interest, but illustrate them with examples of current research in the loop quantum gravity and group field theory approaches to quantum gravity.” In terms of technical difficulty, this talk rates 3.5/5
• Wednesday October 21st 2015 at Geneva – Michael Esfeld (Lausanne): Relationalism about space-time and the essence of matterAbstract: “In this talk, I’ll argue that the essence of matter are spatial relations that connect point particles. Over and above the traditional arguments for relationalism, I’ll lay stress on the claim that Leibniz’ definition of space as the order of what coexists provides for a structural individuation of material objects that respects the principle of the identity of indiscernibles. The spatial relations change. Time then comes in as the order of that change. I’ll sketch out how to obtain geometry and dynamics in a package on that basis. Thus, on the one hand, space emerges from the relations that individuate material objects, and time emerges from the change in these relations. On the other hand, these relations clearly are spatial ones, and the order is temporal not only in the sense of the C-series, but also in the sense of the B-series (and perhaps even the A-series). Finally, I briefly mention reasons to take this framework seriously also when it comes to general relativity and quantum gravity.” In terms of technical difficulty, this talk rates 1/5
Abstract: “It is sometimes claimed that string theory posits a fundamental ontology including extended mereological simples, either in the form of minimum-sized regions of space or of the strings themselves. But there is very little in the actual theory to support this claim, and much that suggests it is false. Extant string theories treat space as a continuum, and strings do not behave like simples.” In terms of technical difficulty, this talk rates 2/5
• Wednesday October 7th 2015 at Geneva – Vincent Lam (Lausanne) (with Christian Wüthrich, Geneva): Functional emergence of spacetime in quantum gravity
Abstract: “Relativistic spacetime, according to many quantum theories of gravity, does not exist, fundamentally. This threatens the very possibility of the empirical confirmation of these theories. Their empirical coherence can be restored by securing the emergence of spacetime from the fundamental non-spatio- temporal structures. Establishing this emergence requires not just mathematical limits and approximations, but also a successful argument that these technical procedures result in appropriately local `beables’. We show in the context of two programs in quantum gravity—loop quantum gravity and causal set theory—that a recovery of the merely functionally relevant features of spacetime suffices to this end.” In terms of technical difficulty, this talk rates 2.5/5