Abstract
A novel description of kinetic theory dynamics is proposed in terms of resummed moments that embed information of both hydrodynamic and non-hydrodynamic modes. The resulting expansion can be used to extend hydrodynamics to higher orders in a consistent and numerically efficient way; at lowest order it reduces to an Israel-Stewart-like theory. This formalism is especially suited to investigate the general problem of particles interacting with fields. We tested the accuracy of this approach against the exact solution of the coupled Boltzmann-Vlasov-Maxwell equations for a plasma in an electromagnetic field undergoing Bjorken-like expansion, including extreme cases characterized by large deviations from local equilibrium and large electric fields. We show that this new resummed method maintains the fast convergence of the traditional method of moments. We also find a new condition, unrelated to Knudsen numbers and pressure corrections, that justifies the truncation of the series even in situations far from local thermal equilibrium.
Highlights
Relativistic hydrodynamics plays a fundamental role in the description of a wide range of physical phenomena, from astrophysical plasmas to heavy-ion collisions [1,2,3]
IV, we propose a new set of moments that resum the contributions of an infinite set of nonhydrodynamic degrees of freedom and show how they can be used to investigate the physics behind the BVM equations efficiently even for massless particle systems
We studied the emergence of hydrodynamics from kinetic theory for an overall electrically neutral system of charged particles described by the Boltzmann-Vlasov-Maxwell equations
Summary
Relativistic hydrodynamics plays a fundamental role in the description of a wide range of physical phenomena, from astrophysical plasmas to heavy-ion collisions [1,2,3]. The first one originates from the Chapman-Enskog expansion [4], which involves a systematic power counting of the gradients of the standard hydrodynamic quantities, i.e., temperature, chemical potential, and velocity fields. An appealing feature of this approach is that the gradient expansion can be performed even around a quantum field theoretical local equilibrium background, i.e., it does not fundamentally require a classical approximation. Such an expansion can be done in the relativistic regime, both in the context of kinetic theory [5] and in the case of strongly coupled relativistic systems, as shown in Refs.
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