“…This means that the spatial derivative u x ( · , t) of the solution (u( · , t), ρ( · , t)) becomes unbounded within finite time, while both u( · , t) H 1 (R) and ρ( · , t) L 2 (R) remain bounded, see e.g. [27,28,29,30,43,44] and the references therein. In addition, energy concentrates on sets of measure zero.…”