10 November 2026
Paper1: T. Jacobson: Gravitation and vacuum entanglement entropy link
Paper2: T. Jacobson: Entanglement Equilibrium and the Einstein Equation link
By Ted Jacobson (online)
24 November 2026
Title: Boltzmann Brains and the Quantum Theory of Everything
Abstract: Physicists don't spend as much time worrying about Boltzmann Brains as they should. The ΛCDM model predicts a future thermal de Sitter phase, which arguably implies fluctuations into minimal systems that dominate the total number of observers in the universe. There is controversy over whether such fluctuations happen - depending on one's views about the foundations of quantum mechanics - and if so, whether they rule out such cosmologies. I will argue that: (1) they don't happen in infinite-dimensional Hilbert space; (2) they do happen in finite-dimensional Hilbert space; (3) they rule out such cosmologies because of cognitive instability, not because of mismatch with the data; and (4) a fine-tuned cyclic cosmology can avoid the problem.
Paper1: K. Boddy, S. Carroll, J. Pollack: De Sitter Space Without Dynamical Quantum Fluctuations link
Paper2: S. Carroll, N. Diachenko, S. Dulani: Toward a Phenomenologically Acceptable Quantum Cyclic Universe link
By Sean Carroll (online)
8 December 2026
Paper: TBD
By TBD
TBD November - December 2026
Paper: TBD
By Caslav Brukner
15 September 2026
Title: A solution to the preferred-basis problem based on the
WAY theorem
Abstract: The preferred-basis problem is an issue that arises in several fields of
quantum foundations: decoherence theory (including its later
developments like quantum Darwinism), consistent histories, the
quantum-to-classical transition, as well as in some discussions about
the measurement problem and the interpretation of QM. From a “3rd person
perspective”, it can be formulated as follows: given the laws of
physics, in which bases do systems preferably entangle and therefore
mutually decohere? That is: about which observables does information
accurately flow between systems? Equivalently, from a “1st person
perspective”, it amounts to understand which measurements can actually
be performed, while the vast majority of bases in the Hilbert space can
not be probed in practice (e.g. Wigner’s non-classical supermeasurement
on his friend). While a variety of models already exist, they remain
arguably insufficient, in the sense that they rely on the choice of some
specific Hamiltonians which clearly favour one basis or another from the
start. In this talk, we propose a universal solution to the
preferred-basis problem, merely assuming the existence of a global
symmetry (a conserved additive charge), based on the Wigner-Araki-Yanase
(WAY) theorem and some basics of quantum reference frames. We further
discuss the implications of this result for the quantum-to-classical
transition.
By Antoine Soulas (online)
29 September 2026
Paper: M. Girard, G. Cheng, CJ Cao: Demystifying Objectivity with Operator Algebra Quantum Error Correction link
By Marin Girard (online)
20 October 2026
Title: Subquantum physics and the Spin-Geometry theorem
Abstract: In standard quantum mechanics the Born rule assigns qubit probabilities as functions of the relative angle between preparation and measurement directions, i.e. real-valued parameters that presuppose classical reference structures of effectively unbounded precision. This idealisation loses its operational footing as soon as physical resources are genuinely finite. I will argue that Penrose's spin-networks, regarded as a finite-resource formulation of quantum mechanics, provide a natural framework within which to confront this regime. Departing from Penrose's original construction, I will show how one can build spin-networks from the bare logic of relations, presupposing no background space, no Hilbert space, no continuum of parameters, and no specified physical content. A uniqueness theorem shows that this primitive starting point determines a single, well-defined combinatorial structure which carries an intrinsic rational probability rule which remains well defined where ordinary probabilistic notions break down, and which demands no a priori separation between a system and its context. Following Moussouris and Penrose, I will then introduce the condition of delta-classicality which singles out the regime in which the probabilities associated with a specific operation are stable under repetition, restoring an operational notion of a repeated experiment and the separation between system and context. I will then introduce the Spin-Geometry Theorem: assuming delta-classicality, the resulting probabilities are parameterised by angles—produced by the bulk of the network---that satisfy every constraint of three-dimensional Euclidean geometry, and the spin-network probability rule reduces to the Born rule. Finally, I will propose a possible interpretation to what a spin-network actually represents, as well as how and when to assign one to a physical situation, and how it can help us investigate what a subquantum theory could be.
By N. Cohen
27 October 2026
Title: Can we turn any Hamiltonian into a lattice theory?
Abstract: We present an algorithm to re-interpret a given Hamiltonian
H as that of a Fermionic lattice theory with a well behaved
one-particle dispersion relation. Applying this algorithm to Gaussian
random H yields a lattice where localized states (wave packets) stay
localized and propagate. We interpret these results as a first step
towards quantum mereology for fields.
Paper: C-J Cao, O. Friedrich, M. Girard, N. Loizeau, A. Singh: Wave packets from the spectrum link
By Oliver Friedrich (online)
Add new papers here
S. Pilatowsky-Cameo, J. Cotler, D. Ranard, J. Riedel: Emergent classicality and wavefunction branching in an isolated quantum many-body system link
J. Kirklin: Emergent Classical Gauge Symmetry from Quantum Entanglement link
S. Carrozza, A. Chatwin-Davies, P. Höhn, F. Mele : A Correspondence Between Quantum Error Correcting Codes and Quantum Reference Frames link
P. Dorau, A. Much: From Quantum Relative Entropy to the Semiclassical Einstein Equations link
C-J Cao, G. Cheng, K. Karthikeyan, C. Li, J. Preskill: State-dependent geometries from magic-enriched quantum codes link
C-J Cao, X-L Qi, B. Swingle, E. Tang: Building bulk geometry from the tensor Radon transform link
C-J Cao, S. Carroll: Bulk entanglement gravity without a boundary: Towards finding Einstein’s equation in Hilbert space link
A. Kiely, D. Chisholm, A. Touil, S. Deffner, G. Landi, S. Campbell: Metrological approach to the emergence of classical objectivity link
A. Kitaev: Almost-idempotent quantum channels and approximate C*-algebras link
X. Jiang, A. Hochrainer, J. Kysela, M. Erhard, X. Gu, Y. Yu, A. Zeilinger: Subjective nature of path information in quantum mechanics link
D. Schmid, Y. Ying, M. Leifer: Coppenhagenish interpretations of quantum mechanics link
L. Catani, M. Leifer, D. Schmid, R. W. Spekkens: Why interference pheonomena do not capture the essense of quantum theory link
S. Carroll, A. Singh: Quantum mereology: Factorizing Hilbert space into subsystems with quasiclassical dynamics link
L.Hausmann, R. Renner: Against probability: A quantum state is more than a list of probability distributions link
N. Bhatta, D. Minic, T. Takeuchi: Dynamics of the Density Cube link