Comment on 'Velocity autocorrelation function in fluctuating hydrodynamics'

For original work see ibid., vol.4, p.L303, 1992. Tsekov and Radoev recently studied the velocity autocorrelation function in a hydrodynamic model using the generalized Langevin equation formalism originally due to Mori and Zwanzig. The more recent recurrence relations formulation of the generalized Langevin equation provides a simplification. It also lends a perspective on the model of Tsekov and Radoev and points out the model's limitations. A refinement of the model is possible by consideration of the Hilbert space geometry as developed by the recurrence relations formulation.