We discuss the observational consistency, possible properties, and detection of collapsed nuclei . These may be considered as elementary particles with mass number and of much smaller radius than ordinary nuclei . The existence of of (perhaps much) lower energy than is observationally consistent if are very long-lived isomers against collapse because of a "saturation" barrier between and . Barrier-penetrability estimates show that sufficiently long lifetimes sec are plausible for . The properties of are discussed using composite baryon and quark models; small charges and hypercharges and, especially, neutral are possible. can be effectively a source or sink of baryons. Some astrophysical implications are briefly discussed, in particular the possible large scale presence of and the possibility that accelerated collapse in massive objects may be a source of energy comparable to the rest mass.
- Received 29 March 1971
- Published in the issue dated 15 September 1971
© 1971 The American Physical Society