High-Frequency Parametric Quenching of Non-Reciprocal Interactions: Dynamic Restoration of PT-Symmetry in Active Matter

This work presents a theoretical framework for dynamically stabilizing active matter systems exhibiting non-reciprocal interactions. Using a non-Hermitian coupled-oscillator model and the method of multiple scales, we show that high-frequency parametric forcing induces an effective renormalization of the non-reciprocal coupling via a zeroth-order Bessel function dependence. This mechanism suppresses the effective asymmetry responsible for Exceptional Point (EP) transitions, driving the system from a broken PT-symmetric phase with complex eigenvalues into a dynamically stabilized regime with purely real eigenvalues. The theory predicts a sharp crossover in the instability growth rate as the forcing amplitude approaches a critical threshold, providing a clear macroscopic signature of dynamic PT-symmetry restoration. A falsifiable experimental protocol based on optically trapped active colloids is proposed to validate the predicted quenching of non-reciprocity. This work provides a general parametric renormalization mechanism for controlling instability and entropy generation in non-equilibrium systems.