We consider a space-fractional wave equation with singular mass term depending on the position and prove that it is very weak well-posed. The uniqueness proved in some appropriate sense. Moreover, we consistency of solution classical solutions when they exist. In order to study behaviour near singularities coefficient, numerical experiments are conducted where appearance wall effect for masses ...

Usin the Painlev test, it is shown that the only interablc nonlinear Klein-Gordon equations ux,=f(u) with f a linear combination of exponentials are the Liouville, sine-Gordon (or sinh-Gordon) and Mikhailov equations. In particular, the double sine-Gordon equation is not interable.

The discrete Klein-Gordon equation on a two-dimensional square lattice satisfies an ` 7→ `∞ dispersive bound with polynomial decay rate |t|−3/4. We determine the shape of the light cone for any choice of the mass parameter and relative propagation speeds along the two coordinate axes. Fundamental solutions experience the least dispersion along four lines interior to the light cone rather than a...