https://doi.org/10.1140/epjc/s10052-025-14028-w
Regular Article - Theoretical Physics
Normal mode analysis within a mutilated relaxation time approximation
Department of Physics, Fuzhou University, 350116, Fujian, China
Received:
27
July
2024
Accepted:
1
March
2025
Published online:
12
March
2025
In this paper, we present a detailed analysis of normal modes based on the Boltzmann equation within the mutilated relaxation time approximation (RTA). Using this linearized effective kinetic description, our analysis encompasses a complete order calculation in wavenumber k, extending the conventional hydrodynamic mode analysis to intermediate and short-wavelength regions. Furthermore, our linear mode analysis can provide a natural classification of kinetic modes into collective modes and non-collective single-particle excitations. In the case of an energy-independent relaxation time, the behavior of hydrodynamic onset transitions is recovered (Romatschke in Eur Phys J C 76:352, 2016). However, for the case with an energy-dependent relaxation time, the distinct classification becomes less clear, as the location of hydrodynamic modes is not well separated from non-hydrodynamic modes.
© The Author(s) 2025
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