Quantum gravity

…S-matrix, cosmological correlators and quantum gravity through presentations and scientific discussion. 30 November 2026 at 09:00 through 4 December at 17:00, Asia/Taipei (UTC+8). Public participant registration closes on 20 November 2026.

Mathematicians and physicists will investigate how topological structures constrain quantum fields and quantum gravity. Properties unchanged by local deformation can impose strong restrictions on microscopic physical theories. The programme brings together expertise in topology and quantum theory to study broader classes of these structures and their implications for physics at very short distance scales.

This Perimeter Institute conference brings together researchers studying quantum reference frames, quantum gravity, quantum foundations and related experiments. Topics include relational observables, quantum information in dynamical spacetime, locality, causality, entanglement, and the operational meaning of observers and subsystems. The meeting runs from 26 to 30 October 2026 in Waterloo, Canada. The organizer provides information for virtual participation.

Consistency requirements on scattering amplitudes can constrain quantum gravity without a perturbative expansion. This talk applies analyticity, crossing and unitarity to maximally supersymmetric gravitational theories in ten and eleven dimensions. It extends bounds from the leading correction to higher-order effective couplings, comparing the allowed regions with string-theory and M-theory predictions. A nearby kink in eleven dimensions suggests a possible route toward characterizing the M-theory scattering matrix through consistency alone.

…The framework generalises smooth quantum mechanics through Hilbert spaces, position and momentum operators, Hamiltonians, unitary dynamics, and observable algebras. A method for bounding mass gaps after symplectic reduction uses the curvature of the unreduced configuration space. Examples include the harmonic oscillator constrained to zero angular momentum, lattice Yang–Mills theory, and fractional-dimensional Laakso spaces. The talk closes with prospective

Vijay Balasubramanian connects quantum chaos with the complexity of time evolution. One approach bounds the smallest circuit needed to simulate physical dynamics; another measures how quickly and ergodically a state explores its accessible Hilbert space. Examples from spin chains, billiards, many-body systems and random matrices distinguish chaotic and integrable behaviour. Applications address geometric conjectures for complexity in quantum gravity and possible failure of effective field theory near spacelike singularities.