On the Problem of Energy Concentration

We discuss the well-known problem of energy concentration, which is the inverse of the strong explosion or the expanding piston problem. Using a number of physical examples, we show that under certain conditions and with certain forces involved in the focusing process, one can achieve the concentration of any amount of energy. First of all, this applies to the gravity force and its manifestation in problems of relativity theory with viscosity and heat conduction taken into account.