Speakers – with video

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.

You are welcome to attend in person, and talks at UIC will 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 L107 (Landolt) if they are on Wednesdays, in room B002 (Bastions) if they are on Thursdays. Our YouTube channel is at: www.youtube.com/c/BeyondspacetimeNet

1 or 5? 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.)

Forthcoming Talks

• 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 4/54(in parts).

• Wednesday 14 March 2018 at UIC – Harvey Brown (Oxford): How Einstein came to employ the action-reaction principle in justifying general relativity

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 2

• Wednesday 28 March 2018 at Geneva – Adam Koberinski (Western): Problems with the cosmological constant problem

• Wednesday 25 April 2018 at Geneva – Lina Jansson (Nottingham): Title to be announced

Past Talks (reverse chronological order)

• 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)1

• 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 1/51

• 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 4/54

• 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 4/54

• 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 4/54

• 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 4/54

• 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 4/54

• 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 4/54

• 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 2

• 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 3/52

• 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 3/52

• 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 3/53

• 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 1/51

• 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 4.5/54.5

• 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 2/52

• 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 5/55

• 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 1/51

• 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  1

• 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 3/53

• 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 4/54

• 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 3/53

• 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 4/54

• 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 2/52

• 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 2/52

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 4/54

• 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 4/54

• Wednesday April 27th 2016 at UIC – Karen CrowtherThe 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  3

• 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  1

(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 4

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  3

• 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 3.5

• 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 2/52

• Wednesday March 2nd 2016 at UIC – DOUBLE HEADER!

(1) Eddy Keming Chen (Rutgers): Our Fundamental Physical Space and the Quantum Wave Function

Abstract: The mathematical structure of realist quantum theories has given rise to an interesting ongoing debate about how our ordinary 3-dimensional space is related to the 3N-dimensional configuration space on which the wave function is defined. Which of the two spaces is our (more) fundamental physical space? In this talk, I review the debate between the 3N-Fundamentalists (wave function realists) and the 3D-Fundamentalists (primitive ontologists). In this talk, I shall focus on an often-cited argument against 3N-Fundamentalism—that it is empirically incoherent (self-undermining), and I will argue that the often-cited defense—Functionalism—falls short of making it empirically coherent. In terms of technical difficulty, this talk rates 2.5/5 2.5

(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 2

• 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 3

• 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 4

• 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 2

• 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 3

• 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 3.5/53.5

• 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 1/51

• Thursday October 8th 2015 at UIC — David Baker (Michigan): Does String Theory Posit Extended Simples? (Slides available here)

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 2

• 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 2.5