Ordinal addition and multiplication can be extended in a natural way to all sets. I survey the structure of the sets under these operations. In particular, the natural partial ordering associated… (More)

This article defines a hierarchy on the hereditarily finite sets which reflects the way sets are built up from the empty set by repeated adjunction, the addition to an already existing set of a… (More)

Editorial Board Marat Arslanov, Kazan John T. Baldwin, Chicago, IL Douglas S. Bridges, Canterbury Armin Hemmerling, Greifswald Ramon Jansana, Barcelona Carl G. Jockusch, Urbana, IL Alexander Kechris,… (More)

This is an area where two different usages of the word “standard” collide: in set theory and in models of arithmetic. The starting point is Vω , the set of hereditarily finite sets. Might this be… (More)