Autocorrelation of density fluctuations for thermally relativistic fluids

The autocorrelation of density fluctuations for thermally relativistic fluids is formulated on the basis of the relativistic Navier-Stokes-Fourier equation under the static equilibrium state. The autocorrelation of density fluctuations for thermally relativistic fluids, obtained theoretically, is compared with the autocorrelation of density fluctuations for thermally relativistic fluids, calculated using the stochastic relativistic Boltzmann equation on the basis of the direct simulation Monte Carlo method. The theoretical result of the autocorrelation of density fluctuations for thermally relativistic fluids on the basis of the relativistic Navier-Stokes-Fourier equation gives good agreement with the numerical result of the autocorrelation of density fluctuations for thermally relativistic fluids in the lowest wave number, because we calculated the autocorrelation of density fluctuations for thermally relativistic fluids under the transition regime between the rarefied and continuum regimes.