Causal Diffusion and the Survival of Charge Fluctuations in Nuclear
Collisions.
Diffusion may obliterate fluctuation signals of the QCD phase transition
in nuclear collisions at SPS and RHIC energies. We propose a hyperbolic
diffusion equation to study the dissipation of net charge fluctuations.
This equation is needed in a relativistic context, because the classic
parabolic diffusion equation violates causality. We find that causality
substantially limits the extent to which diffusion can dissipate these
fluctuations.