Flexible polyhedra in Minkowski 3-space (Q1401511)

The author considers flexibility of polyhedra in a Minkowski 3-space, i.e., in a linear space consisting of all ordered triples \((x_1,x_2, x_3)\) endowed with the scalar product \((x,y)=x_1y_1 +x_2y_2-x_3y_3\). He confirms the existence of (non-immersed) flexible polyhedra in such a space, and that any of them preserves the (generalized) volume and the (total) mean curvature during a flex. His arguments are based on the notion of an angle in a Minkowski 2-space.