Entropy thermalization in quantum chaotic systems with energy conservation

Let a quantum system evolve under a time-independent Hamiltonian, and let $A$ be a subsystem. Entropy thermalization means that, after long-time evolution, the entropy of $A$ agrees to leading order in the size of $A$ with the thermodynamic entropy of $A$ at the same energy. A local conserved quantity is a quantity whose conservation law applies within the subsystem structure, and suppose that energy is the only such quantity. Entropy-thermalization conjecture. Entropy thermalizes in quantum chaotic systems where energy is the only local conserved quantity. This proposes a fundamental quantum-mechanical explanation of thermalization, beyond the ergodic hypothesis or equal a priori probabilities. The statement is presented as widely believed in the source, but no resolution is given here.