  In a quantum field theory, apparent thermalization can be a consequence of
entanglement as opposed to scatterings. We discuss here how this can help to
explain open puzzles such as the success of thermal models in electron-positron
collisions. It turns out that an expanding relativistic string described by the
Schwinger model (which also underlies the Lund model) has at early times an
entanglement entropy that is extensive in rapidity. At these early times, the
reduced density operator is of thermal form, with an entanglement temperature
$T_\tau=\hbar/(2\pi k_B\tau)$, even in the absence of any scatterings.
