Ultraperipheral nuclear interactions

Long-distance ultraperipheral collisions of two relativistic ions are considered. Clouds of photons surrounding the ions are responsible for their distant electromagnetic interaction. The perturbative approach and the method of equivalent photons are described. It is shown that the total cross section of these collisions rapidly increases with an energy increase and is especially large for heavy ions. Some experimental data and their comparison with theoretical approaches are described. Further proposals are discussed.