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arXiv · 2604.27459

Galilean boost invariance does not survive the trace: symmetry breaking in open quantum systems

Leonardo F. Calderón·Esteban Marulanda·Santiago Morales·Leonardo A. Pachón
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Abstract

Tracing out a Galilean-invariant Caldeira-Leggett environment breaks Galilean boost covariance of the reduced dynamics, while spatial translations and rotations survive intact. An operator-level analysis of the exact Hu-Paz-Zhang master equation localizes the violation entirely in the dissipative anticommutator term, scaling with the damping coefficient $\Gamma(t)f(t)$. The fluctuation-dissipation theorem ties this coefficient to the absorptive bath response that drives equilibrium momentum diffusion, so for any non-trivial bath spectral density bilinear-coupled Galilean invariance, the fluctuation-dissipation theorem, and reduced boost covariance cannot hold simultaneously. The stochastic decomposition of the influence functional extends the mechanism beyond the quadratic regime. The dimensionless ratio $\hbar\gamma/k_\mathrm{B} T$ delineates the crossover: cold atoms in dissipative optical lattices and ultracold molecules sit at its edge. Parametric driving offers a one-directional escape: the squeezing rate that protects nonequilibrium entanglement above the standard quantum limit also suppresses boost-breaking over a driving cycle.

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Leonardo F. Calderón, Esteban Marulanda, Santiago Morales, Leonardo A. Pachón. 2026-04-30. Galilean boost invariance does not survive the trace: symmetry breaking in open quantum systems. https://arxiv.org/abs/2604.27459

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