deletions | additions       diff --git a/Payam.tex b/Payam.tex  index da59f40..16aa947 100644  --- a/Payam.tex  +++ b/Payam.tex 
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\begin{itemize}  \item No! They are measuring different things. Payam's $t_{\rm h}$ is considering the diffusion of momentum information about a particle (I think this is the characteristic time in the decay of the velocity autocorrelation). My $t_{\rm h}$ is about pure information flow.  \item Why does the hydrodynamic disturbance travel diffusively rather than at the sound speed?  \item Some reading about propagation of hydrodynamic information:\\  \citet{1995PhyA..214..185E},  \citet{Espanol_Rubio_Zuniga_1995} for evidence of sound-wave propagation;\\