Boundary R'enyi oscillations in the open XX chain
The authors derive closed-form asymptotic formulas for Rényi entanglement entropies of open XX spin-1/2 chains by mapping their determinant structure to a Hankel determinant with a positive weight. This yields explicit oscillatory amplitudes and phases, providing detailed predictions for boundary blocks and the hard-edge crossover. The framework also clarifies symmetry-resolved entanglement properties.