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).
More info in Speakers tab above.
• 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.
We are very sad to learn of the death of Joseph Polchinski. His work, including his String Theory textbook, is very important to many philosophers thinking about string theory, and he was generous with his time and intellect with our community. He will be missed.
The statement from UCSB is here: https://chancellor.ucsb.edu/memos/?2.2.2018.Sad.News…Professor.Emeritus.Joseph.Polchinski
The terrific paper that he wrote for Studies in History and Philosophy of Modern Physics is here: https://arxiv.org/abs/1412.5704
The videos of the December talks in Geneva by Karen Crowther and Vincent Lam have just been posted to our YouTube channel. Please visit https://www.youtube.com/channel/UC_VhTJBl6Mpmfjj5q832rjg to find them! We apologize for the poor sound quality in the Crowther video.
After the success of our Summer School two years ago, we are very pleased to announce that the Space and Time After Quantum Gravity project will be a major component of the First Biennial Midwest Summer School in Philosophy of Physics, to be held in Chicago in late July. We hope that there will be no cost to students to attend.
More details and a call for applications can be found above or here: https://beyondspacetime.net/summer-school-2018/
Please join us!
Science journalist George Musser sat down with philosopher of physics Richard Healey to discuss the meaning of gauge theories, the basis of our modern understanding of force and matter. For all their predictive power, these theories leave us in the dark about the basic ingredients of the physical world.
On our channel or at https://www.youtube.com/channel/UCMmbfiYIu77cn64Qsjrzh1Q.
• 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
With apologies for the delay, we have now posted Laura Ruetsche’s talk from the spring. Find it above under speakers, or on our YouTube channel here: Renormalization Group Realism: An Unduly Skeptical Review
On Wednesday 15 November 2017 at UIC (11.15am local time), Laurent Freidel (Perimeter) will speak on 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
Full details above on the speakers page.