91 90 Principal Scientist Profiles Holger Gies Holger Gies Principal Scientist Profiles PROFESSOR OF QUANTUM THEORY AT INSTITUTE OF THEORETICAL PHYSICS Prof. Gies is the spokesperson of the research unit FOR 2783 on “Probing the Quantum Vacuum at the High Intensity Frontier” and of the research training group GRK 2522 on“Strong Dynamics and Criticality of Quantum and Gravitational Systems”, both funded by the German Research Foundation (DFG). He serves as a member of the extended directorate of the Helmholtz Institute Jena and on the board of the Helmholtz Research School of Advanced Photon Science. HOLGER GIES RESEARCH AREAS Prof. Gies investigates the potential of using light as a probe for fundamental physics. Research thrusts include: • Properties of light induced by quantum or thermal fluctuations • Quantum phenomena at highest laser intensities • Light-induced particle production • Light propagation in modified quantum vacua • Optical searches for exotic particles • Light-matter interactions out of equilibrium TEACHING FIELDS Prof. Gies provides advanced theory courses, supporting the training of young developing researchers during their early project phases. He gives courses in: • Quantum field theory and quantum mechanics • Strong-field and quantum vacuum physics RESEARCH METHODS Prof. Gies develops and applies a wide range of theoretical methods to describe quantum correlations of light and matter including: • Perturbative effective actions and correlation functions • Analytical and computer-algebraic field theory methods • Numerical worldline algorithms for inhomogeneous electromagnetic fields • Non-equilibrium quantum transport equations • Non-perturbative renormalization flows RECENT RESEARCH RESULTS Dealing with quantum processes in realistic inhomogeneous fields requires a thorough understanding of quantum fluctuations in general field profiles. The quantum theory group is strongly involved in method development for the efficient determination and prediction of salient signatures of the quantum world in upcoming strong-field experiments. For instance, the group has developed the worldline Monte Carlo technique which currently is the only theoretical tool in practice which is capable of determining quantum properties of light in general strong-field backgrounds. A main topic deals with the potential of upcoming highintensity laser facilities as discovery machines of fluctuation induced vacuum nonlinearities. In close collaboration with experimental colleagues, the group has developed general purpose methods to efficiently describe quantum vacuum phenomena in focused laser pulses [1], which has lead to the proposal of a new experimental detection scheme [2], suggesting novel inelastic processes as a key signature. This potential signature of light scattering off a high-intensity region is a prototypical example of a new kind of all-optical phenomena at the high-intensity frontier that has the potential to explore this new regime of physics for the first time. The group also addresses issues of theoretical consistency of quantum electrodynamics (QED) as the currently most fundamental description of light-matter interactions. This has lead to a recent proposal of a novel high-energy completion of QED by means of a scenario based on the concept of asymptotic safety [3]. This new line of research has provided first evidence for the existence of a so far undiscovered universality class that features the existence of high-energy complete“lines of constant physics”and has the potential to solve a decades-old consistency puzzle of QED. QUANTUM ENERGY DENSITIES OF THE PHOTON FIELD IN MICRO- AND NANOSTRUCTURES Photonic quantum fluctuations in structured geometries can be investigated with the worldline Monte Carlo method, developed by the Quantum Theory Group. Quantum fluctuations are mapped out by their random spacetime trajectories inside a given geometric configuration, such as the experimentally often used sphere-plate configuration. The number of interactions between the quantum trajectories of the photon field and the material are a quantitative measure for the fluctuation-induced energy density inside the geometry (blue shining region). Recent algorithmic developments make it now possible to study the quantum-modified propagation properties of light within such a geometry. [1] Blinne et al., Phys.Rev. D 99, 016006 (2019). [2] Karbstein et al., Phys. Rev. Lett. 123, 091802 (2019). [3] Gies et al., Eur. Phys. J. C80, 607 (2020). Contact: Phone: + 49 3641 9-47190 Email: holger.gies@uni-jena.de
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