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Description
Summary
We calculate all diffusion constants of the conserved baryon, electric and strangeness charge in
hot relativistic multi-component systems using kinetic theory. Applying the algorithm for massive
pions, kaons, nucleons, lambda- and sigma-baryons, with resonance cross sections when possible, we
present for the first time realistic values for the hadronic diffusion coefficient matrix. These values
can readily be used in dissipative hydrodynamic calculations for baryon rich systems and serve
as benchmark for other theoretical approaches. In order to put the hadronic results in context, we
compute the diffusion matrix for the quark-gluon plasma (QGP). To this end we use massless quarks
and gluons, fixing the shear viscosity to the lower bound of $1/4\pi$. For all but the baryon-electric
cross diffusion coefficient, we find that the QGP result matches the hadronic result around the phase
transition temperature. All results fulfill the Onsager theorem and the qualitative similarity to the
relaxation time approximation.
We find that the baryon diffusion current depends strongly on baryon chemical potential, and, we
see a comparable strength of the baryon-strange cross diffusion to baryon diffusion. Electric current
is equally strongly affected from baryon, electric and strangeness gradients, whereas strangeness
currents depend mostly on strange and baryon gradients. These results imply, that calculations
involving only the diagonal diffusion effects are incomplete.
