Thermalization of closed quantum systems is central to the modern understanding of matter, from ultracold to ultrahot. High-TheQ studies thermalization of quantum fields excited by nuclear collisions at RHIC and LHC to energy densities equivalent to trillions of Kelvins. In such extreme environments hadrons melt and the equilibrium state is the quark-gluon plasma. Theoretical control over thermalization at high energies is crucially needed for understanding when and how this equilibrium phase emerges in the experiments.

The current theoretical paradigm for thermalization in quantum chromodynamics is based on hydrodynamic and non-thermal attractors (fixed points). They are novel examples of universal dynamics of non-equilibrium quantum fields. Both were found in idealized settings of nuclear collisions with high degree of symmetries and in particular corners of a microscopic parameter space. The goal of High-TheQ is to understand thermalization in quantum field theory beyond these idealizations. Do hydrodynamic attractors appear for off-central nuclear collisions? Is there a gravity dual to a non-thermal attractor? Do non-thermal and hydrodynamic attractors have a common origin, such as spontaneous symmetry breaking?