Jump to content

Nice name

From Wikipedia, the free encyclopedia

In set theory, a nice name is used in forcing to impose an upper bound on the number of subsets in the generic model. It is used in the context of forcing to prove independence results in set theory such as Easton's theorem.

Formal definition

[edit]

Let ZFC be transitive, a forcing notion in , and suppose is generic over .

Then for any -name in , we say that is a nice name for a subset of if is a -name satisfying the following properties:

(1)

(2) For all -names , forms an antichain.

(3) (Natural addition): If , then there exists in such that .

References

[edit]
  • Kunen, Kenneth (1980). Set theory: an introduction to independence proofs. Studies in logic and the foundations of mathematics. Vol. 102. Elsevier. p. 208. ISBN 0-444-85401-0.