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2023 John William Strutt, Lord Rayleigh Medal and Prize

Professor Nikolas Mavromatos for fundamental contributions to theoretical physics, especially the suggestion of quantum gravity-induced modifications of the vacuum optical properties, a proposition that led to a new arena of theoretical and experimental investigation.

Nick Mavromatos award winner

Professor Nikolas Mavromatos pioneered the exploration of properties of quantum spacetimes and resulting tests of Lorentz invariance using intense extragalactic light sources as probes. Using string models, he and his collaborators have made the groundbreaking discovery that quantum gravity could modify the optical properties of the vacuum, a proposition that led to a new arena of theoretical and experimental investigation. This came from Mavromatos’ idea that time in (non-critical) string theory could be the result of violation of (conformal) symmetries. He demonstrated that such violations are linked to a ‘medium’ of spacetime defects, which could characterize theories of quantum gravity (QG), including strings. Using time-space stringy uncertainty relations, he has shown that the associated spontaneous Lorentz-invariance violation (LIV) implies that detected photons emitted from intense cosmic sources, such as gamma ray bursters or active galactic nuclei, will be delayed more or less depending on their higher or lower energies. Although originating from string theories, this idea influenced the development of other LIV theories, but the resulting phenomenology is model independent. A nice analogy for the variation of photon velocity with energy is provided by observation of boats (photons) in rough seas (medium of defects). If the boat length is much larger than the wavelength, the boat is only slightly impeded, while boats of considerably smaller length than the wavelength are delayed significantly.

Following this suggestion and under his leadership, many experiments explore the quantum properties of spacetimes and test Lorentz invariance, using intense extragalactic light sources as probes. His work has contradicted the view that empirical tests of QG and the structure of spacetime are impossible due to the unattainable energies of the Planck scale. Importantly, he and his coworkers have placed limits on LIV and suggested important tests of the quantum universe using astrophysical data, notably in a Nature paper with over 1200 citations. Mavromatos has coauthored an experimental paper with the MAGIC Collaboration. He has also pioneered other possible manifestations of QG in particle accelerators (he coauthored a highly cited experimental paper with the CPLEAR Collaboration). Recently, Mavromatos and collaborators have embarked on a study testing photon and graviton QG-induced modified dispersion relations, using the new interferometric network technology that emerges from the Laser Interferometer Gravitational-Wave Observatory discovery of gravitational waves.