In search of spontaneous positron creation

The recent experiments investigating the behavior of the electron-positron field in strong external electromagnetic fields is reviewed. In particular, the search for spontaneous positron creation in superheavy collision systems is discussed. A striking new result emerging from this search is the observation of narrow peaked structures in the positron spectra whose origin cannot be associated with the established dynamic mechanisms of positron production involving Coulomb trajectories only. The possibility that these peaks may be signatures for the spontaneous decay of the vacuum and for the formation of metastable giant nuclear complexes is considered in the content of recent experimental results. 52 references, 23 figures