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Collective Dynamics in Little Big Bangs

6–8 Aug 2025
Europe/Zurich timezone

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Shakhov collision model in relativistic kinetic theory

6 Aug 2025, 11:25
25m

Speaker

Dr Victor Ambrus (West University of Timișoara)

Description

We present a systematic method to construct the Shakhov collision term, as an extension of the relaxation time approximation (RTA) of the Boltzmann colllision term (1). Our construction is based on the collision matrix in the method of moments and allows an increasing number of first- and second-order transport coefficients to be separately tuned (2). The talk is focussed on the ultrarelativistic gas of hard spheres, for which the transport coefficients are known (3). Numerical simulations show that good agreement with the first-principles BAMPS results reported by DNBMXRG (4) can be achieved only if (almost) all second-order transport coefficients are correctly recovered (2) (see Figure).

Comparison between BAMPS data (black circles) for the Sod shock tube problem, the Anderson-Witting RTA model (AW) and various Shakhov models ($N_1$, $N_2$, $s_1$, $s_2$) with vector and tensor collision matrices of sizes $(N_1 + s_1)^2$ and $(N_2+s_2)^2$, respectively.

(1) VEA, E. Molnar, Phys. Lett. B 855 (2024) 138795. DOI: 10.1016/j.physletb.2024.138795.
(2) VEA, D. Wagner, Phys. Rev. D 110 (2024) 056002. DOI: 10.1103/PhysRevD.110.056002.
(3) D. Wagner, VEA, E. Molnar, Phys. Rev. D 109 (2024) 056018. DOI: 10.1103/PhysRevD.109.056018.
(4) G. S. Denicol et al, Phys. Rev. D 89 (2014) 074005. DOI: 10.1103/PhysRevD.89.074005.

Presentation materials

Ambrus_Shakhov.pdf