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| Main Authors: | , , |
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| Format: | Preprint |
| Published: |
2026
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2601.16625 |
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Table of Contents:
- We investigate the far-from-equilibrium dynamics and transport properties of a relativistic massive gas obeying Maxwell-Boltzmann (MB), Bose-Einstein (BE), and Fermi-Dirac (FD) statistics undergoing a boost-invariant Bjorken expansion. We solve the relativistic Boltzmann equation in the relaxation-time approximation (RTA) using the method of moments. We focus on the time evolution of the trace of the energy-momentum tensor $Θ^μ{}_μ$ and the bulk viscous pressure $Π$, which are key diagnostics of conformal-symmetry breaking in the rapidly evolving fireball created in heavy-ion collisions. We find that the non-equilibrium quantity $Θ^μ{}_μ/T^{4}$ exhibits a non-monotonic time dependence, with a local maximum at early times and a pronounced dip around the characteristic relaxation time scale $τ_{R}$. We further show that the scaled bulk pressure $Π/P_{0}$, where $P_{0}$ denotes the isotropic equilibrium pressure, depends sensitively on the particle statistics. In addition, increasing the initial chemical potential enhances the magnitudes of both $Π$ and $Θ^μ{}_μ/T^{4}$. Finally, by initializing the system with random non-equilibrium configurations, we demonstrate that the evolution of the scaled bulk pressure and the pressure anisotropy converges to a common late-time solution.