The study is proposed of a group of phenomena so far not systematically treated. The term cooperative phenomena is adopted because of the fact that these phenomena are caused by interactions of a great number of elementary particles such as electrons, atoms, etc. These interactions extend over distances which are enormously greater than the usual action radii of the elementary particles. A brief survey of some possible cooperative phenomena in static and in stationary systems is given and their importance in physics, astrophysics, and biology is pointed out. Incidentally a generalization of thermodynamics from static systems to stationary systems is discussed. The view is advanced that the existence of crystals is due to certain cooperative phenomena which fact would in general necessitate the existence of a secondary structure of crystals. The various general contentions and conclusions of this paper are illustrated and applied in the case of ferromagnetism.

• Received 23 December 1932

DOI:https://doi.org/10.1103/PhysRev.43.270