| We study the velocity autocorrelation function (VACF) of a driven granular fluid in the stationary state in 3 dimensions with the help of event driven molecular dynamic simulations. As the critical volume fraction of the glass transition in the corresponding elastic fluid is approached, we observe pronounced cage effects in the VACF as well as a strong decrease of the diffusion coefficient, depending on the strength of the inelasticity. At moderate densities the VACF is shown to decay algebraically in time like t-3/2 if momentum is conserved locally, and like t-1 if momentum is not conserved by the driving. A simple scaling argument supports the observed long-time tails. |
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