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Open quantum system approach to the Unruh-DeWitt detector in impulsive plane wave spacetimes

Hing-Tong Cho*

  • *Contact author: htcho@mail.tku.edu.tw
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Phys. Rev. D 114, 084064 – Published 21 October, 2026

DOI: https://doi.org/10.1103/qmzv-5m4b

Abstract

In this paper, we employ the open quantum system framework with the influence functional formalism to nonperturbatively analyze the response of an Unruh-DeWitt detector modeled as a harmonic oscillator which interacts with a massless scalar field in impulsive plane wave spacetimes. Subtracting the Minkowski results, we obtain the expectation values for ⟨Q2⟩, ⟨P2⟩, and ⟨{Q,P}⟩, along with transition probabilities P0→1 from ground state to the first excited state of the detector due to the influence of the wave. Explicit calculations are performed for both a pure gravitational wave (vanishing Ricci tensor) and a null electromagnetic wave (vanishing Weyl tensor). In both scenarios, the wave suppresses excitation transitions. Since our approach is nonperturbative, we are able to consider cases with both weak and strong coupling constants.

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Phys. Rev. D 114, 084064– Published 21 October, 2026
  • Received 21 August 2026
  • Accepted 8 October 2026
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