The concept of prime ends was introduced by Constantin Carathéodory to describe the boundary behavior of conformal maps in the complex plane in geometric terms. The theory has been generalized to more general open sets. The expository paper of Epstein (1981) provides a good account of this theory with complete proofs: it also introduces a definition which make sense in any open set and dimension. Also Milnor (2006) gives an accessible introduction to prime ends in the context of complex dynamical systems.
The set of prime ends of the domain B is the set of equivalence classes of chains of arcs converging to a point on the boundary of B.
Carathéodory's principal theorem on the correspondence between boundaries under conformal mappings can be expressed as follows:
- Epstein, D. B. A. (3 May 1981), "Prime Ends", Proceedings of the London Mathematical Society, Oxford: Oxford University Press, s3–42 (3): 385–414, doi:10.1112/plms/s3-42.3.385, MR 0614728, Zbl 0491.30027, (subscription required ()).
- John, Milnor (2006) , Dynamics in one complex variable, Annals of Mathematics Studies, 160 (3rd ed.), Princeton, NJ: Princeton University Press, pp. viii+304, doi:10.1515/9781400835539, ISBN 0-691-12488-4, MR 2193309, Zbl 1281.37001 – via De Gruyter, (subscription required ()), ISBN 978-0-691-12488-9,
- Hazewinkel, Michiel, ed. (2001), "Limit elements", Encyclopedia of Mathematics, Springer, ISBN 978-1-55608-010-4