Momentum-Resolved Probing of Lorentz-Violating Dispersion Relations via Unruh-DeWitt Detector

Abstract: Inspired by quantum gravity frameworks predicting Planck-scale deviations from Lorentz invariance, we probe Lorentz symmetry violation via modified dispersion relations $\omega_{|\textbf{k}|}$. Departing from conventional approaches, we employ an Unruh-DeWitt detector to probe energy-dependent modifications to the dispersion relations. Two key methodological advances are introduced: (i) a generalized formulation for detector acceleration without assuming specific dispersion relations, and (ii) a momentum-resolved detection paradigm enabling spectral decomposition of $\omega_{|\textbf{k}|}$ through localized momentum-shell integration. By restricting detector-field interactions to narrow spectral windows and performing iterative Taylor expansions around reference momenta $|\textbf{k}0|$, we derive coefficients encoding derivatives of $\omega{|\textbf{k}|}$, reconstructing its global profile via momentum-space tomography. The analysis reveals how deviations from linear dispersion relations disrupt the thermal character of the Unruh effect, while perturbative modifications preserve thermality at low energies. This approach offers a scalable method to test Lorentz symmetry violation across energy scales, and establishes a foundation for experimental verification of Planck-scale relics through high-precision spectral measurements.