ИСТИНА

The famous Maxwell formula provides a tool to calculate the length a local minimal tree in the Euclidean plane. An interesting question is to find a generalization of this formula for the case of normed spaces. It turns out that Maxwell formula becomes invalid for local minimal trees in the case of nonsmoothed normed spaces. On the other hand, there is an analogue of Maxwell formula for extremal trees in an arbitrary normed space. In our talk we present the formula and other results on extremal and local minimal trees in normed spaces.