Entropy from scattering in weakly interacting systems

• URL: http://arxiv.org/abs/2506.19127v3
• Date: Thu, 04 Sep 2025 23:59:31 GMT
• Title: Entropy from scattering in weakly interacting systems
• Authors: Duncan MacIntyre, Gordon W. Semenoff,
• Abstract summary: We find surprisingly simple criteria for the initial state and the S matrix that guarantee that the subsystem entropy increases.<n>The class of initial states that meet these criteria are more correlated than simple product states of the subsystems.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Perturbation theory is used to investigate the evolution of the von Neumann entropy of a subsystem of a bipartite quantum system under the action of a unitary matrix, in the limit where that matrix is close to the unit matrix. The physical context for such process would be scattering with weak short-ranged interactions where the unitary matrix is the S matrix. We find surprisingly simple criteria for the initial state and the S matrix that guarantee that the subsystem entropy increases. The class of initial states that meet these criteria are more correlated than simple product states of the subsystems. They form a subclass of the set of all separable states, and they can therefore be assembled by classical processes alone.

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