Blow up of solutions to the second sound equation in one space dimension

In this paper, we study blow ups of solutions to the second sound equation ∂2 t u= u∂x(u∂xu), which is more natural than the second sound equation in Landau–Lifshitz’s text in large time. We assume that the initial data satisfies u(0, x)≥ δ > 0 for some δ. We give sufficient conditions that two types of blow up occur: one of the two types is that L∞-norm of ∂tu or ∂xu goes up to the infinity; the other type is that u vanishes, that is, the equation degenerates.