Intrinsic Limits on Quantum Coherence: Characteristic Velocity, Frequency, and Geometric Thresholds.

Quantum coherence, the hallmark of quantum superposition and interference, is not only limited by environmental decoherence but also by intrinsic quantum properties and spacetime geometry. In this work, we rigorously derive characteristic velocity scales and critical frequencies that define the persistence of coherence, based on the Heisenberg Uncertainty Principle and wave packet dynamics. We further extend the framework to include potential influences of spacetime curvature, introducing a geometric length scale relevant to coherence persistence. This unified approach offers quantitative thresholds for coherence in ultracold atoms, neutron interferometry, nanomechanical resonators, and extreme astrophysical environments. Our results provide insights into the interplay between quantum mechanics, spatial confinement, and geometry, offering guidance for experimental design and quantum technology development.