Quantum internal vibrations in macroscopic systems with classical centers of mass
Gabriel H. S. Aguiar, George E. A. Matsas
TL;DR
This work examines how classical center-of-mass behavior can emerge in macroscopic systems while internal degrees of freedom preserve quantum coherence. It proposes a Lorentz-invariant gravitational self-decoherence mechanism in which the c.m. interacts with a virtual clone via a regularized gravitational potential, yielding mass-dependent classicalization that intensifies near the Planck mass $M_\text{P}$. The authors extend the framework to internal-vibration modes and show, using perturbation theory, that modes with $\omega \ll \Omega_\text{P}$ maintain high purity $\eta \approx 1$ and fidelity $F \approx 1$, indicating retained quantumness despite a classical c.m. These results align with experiments showing quantum coherence in internal degrees of freedom within macroscopic systems, and they underscore a separation of scales at Planckian masses while highlighting experimental paths to probe c.m. superpositions for $m \gtrsim M_\text{P}$ to test planckian spacetime structure.
Abstract
Harmonizing classical and quantum worlds is a major challenge for modern physics. A significant portion of the scientific community supports the notion that classical mechanics is an effective theory that arises from quantum mechanics. Recently, the present authors have argued that this should not be the case, as quantum mechanics is not trustworthy for describing the center of mass of systems with masses $m$ much larger than the Planck mass $M_\text{P}$. In this vein, a simple gravitational self-decoherence model was proposed, describing how the center of mass of quantum systems would classicalize for $m \sim M_\text{P}$. Here, we show that our model does not prevent macroscopic systems (with classical centers of mass) from harboring quantum internal vibrations (as has been observed in the laboratory).