Hi there, I am always confusing in the difference between diffusive and ballistic transport. My understanding on the diffusive transport is from it's name, particles diffuse from the high density region into the low density region. I think the diffusion happens towards all direction, is it why usually it is formulated as ##\langle x^2(t) \rangle = Dt## ? For the ballistic transport, it is very confusing where is the term ballistic from. But my understanding is the transport is linear, is that correct? I saw that in some article, there mentions transport in momentum. It looks like that the ballistic transport corresponding to quadratic growth of kinetic energy. I don't understand why but if that's the case, how does it look like for energy for diffusive transport in momentum?