Entanglement, thermalization and hadronisation for SU(N) gauge theories

• Applicant: Professor Dr. Andreas Schäfer
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 553079183

Connections between quantum field theory, gravity, and quantum information science form an increasingly active field of research. Physicists have learned to combine techniques from different subfields in an efficient manner, leading to rapid progress in our understanding of quantum phenomena, from the structure of ground states to the dynamics of quantum systems far off equilibrium. Examples include the emergence of thermal behavior in isolated quantum systems, encapsulated in the Eigenstate Thermalization Hypothesis (ETH), the duality between quantum fields and higher-dimensional gravity, commonly encoded in the term "holography", and insight that entanglement of quantum states can serve as a powerful tool in the transport and processing of quantum information. Our proposal belongs into this large domain, but focuses on two selected aspects with broad relevance to phenomena in nuclear and particle physics that remain poorly understood: One is the time evolution of isolated quantum systems and their possible thermalization; the other is the break-up of highly excited, strongly interacting, transient quantum systems into individual particles that are eventually detected separately. A process in which both tracks comprise primary aspects of the dynamics are highly energetic collisions between complex nuclei, commonly called relativistic heavy ion collisions (HICs). HICs in the ultra-high vacuum of particle colliders create among the best isolated quantum systems one can imagine. Experiments have collected an enormous amount of detailed data that are already available for tests of theoretical ideas, and specific new data can be obtained in the future. In particular, several stages of a HIC that are commonly described by statistical methods remain poorly understood at the quantum level. The holographic duality between thermalization in HICs and the formation of a black brane in Anti de Sitter (AdS) space is conceptually well established, enabling exact numerical treatment of strongly coupled models of quantum gauge theories. We plan to explore a large number of aspects: With numerical simulations of SU(2) gauge theory we want to map the range of validity of ETH and clarify in which sense thermalization can occur. We also want to clarify whether SU(2) has Quantum Many Body Scars. In addition, we want to improve the techniques of such simulations, e.g. to treat three space dimensions and/or fermions in an efficient manner. The holographic description we want to continue beyond thermalization to cover also hadronisation. Finally we want to collaborate with experts in quantum computing on these topics.

• DFG Programme: Research Grants
• International Connection: USA
• Partner Organisation: National Science Foundation (NSF)
• Cooperation Partner: Professor Dr. Berndt Müller