Physikalisches Kolloquium: Dr. Wolfgang Wieland – On the Light Cone Structure of Quantum Spacetime Geometry

Titel: On the Light Cone Structure of Quantum Spacetime Geometry

Abstract:
In Einstein's theory of general relativity, the causal structure of spacetime is itself dynamical. Causality is encoded into the geometry of light cones that bend under the influence of gravity. Quantum theory, on the other hand, tells us that nature is intrinsically probabilistic. A sharply defined causal structure, as it appears in classical general relativity, contradicts quantum theory. A more general framework is needed. This colloquium outlines a research programme in quantum gravity to develop a mathematical understanding of the causal structure at the quantum level. This is, in fact, a problem common to different approaches to quantum gravity, from holography, to the perturbative S-matrix approach and loop quantum gravity. After a brief introduction into the conceptual aspects of the topic, several recent results on this frontier will be presented. First, the construction of physical observables using the light cone geometry is explained. Then, building upon earlier results in loop quantum gravity, the description is taken to the quantum level. Finally, the talk presents recent developments on how a fundamental quantum discreteness of geometry can alter the spectrum of highly luminous gravitational wave events.
The talk is based on arXiv:arXiv:2504.10802,2402.12578, 2401.17491, 2104.05803.

Sprecher / Speaker: Dr. Wolfgang Wieland (Heisenberg Fellow, FAU)
Kontakt / Contact: Department Physik, Prof. Dr. K. Giesel