Figure 1
From: Quantum Thermalization and the Expansion of Atomic Clouds
Expansion of an atomic cloud into the vacuum. Initially we prepare an one-dimensional atomic cloud in region A (|x| < 5), at inverse temperature β = 0.01, with particle density n = 0.5. On the left we show the energy density as a function of position x and time t, following exact quantum evolution. On the right we show the density of particles n A (t) in region A. The full quantum evolution is correctly represented by a classical distribution of particle positions and velocities n(x, v, t) whose time evolution is given by ballistic motion, n(x, v, t) = n(x − vt, v, 0). At late times, the particle density in region A decays as n A ~ 1/t, in the right graph shown as a dashed line.
