Thermalization of quantum many-body scars in kinetically constrained systems

The phenomenon of quantum many-body scars (QMBS) has been studied both theoretically and experimentally, due to its unusual violation of the eigenstate thermalization hypothesis (ETH). In this paper, we extend the ETH to a description based on the grand canonical ensemble to depict the thermal properties of QMBS models. For this purpose, we embed the dynamics of kinetically constrained systems within a Lindblad-like master equation, and demonstrate that the violation of the ETH by scar eigenstates is related to their slow decay in the corresponding dissipative process. Within this open system description, we reformulate the ETH to demonstrate that both scar eigenstates and thermal ones exhibit thermalization governed by grand canonical statistics. Consequently, our revised ETH unifies scars and thermal states under a cohesive thermodynamic rule. Our work resolves the fundamental tension between constraint-induced nonergodicity and thermalization paradigms, establishing a unified route to generalized thermalization in quantum many-body systems.