Common integrals in quantum field theory

In set theory, a branch of mathematics, the condensation lemma is a result about sets in the constructible universe.

It states that if X is a transitive set and is an elementary submodel of some level of the constructible hierarchy L_α, that is, $(X,\in )\prec (L_{\alpha },\in )$, then in fact there is some ordinal $\beta \le \alpha$ such that $X=L_{\beta }$.

More can be said: If X is not transitive, then its transitive collapse is equal to some $L_{\beta }$, and the hypothesis of elementarity can be weakened to elementarity only for formulas which are ${\mathrm{\Sigma }}_1$ in the Lévy hierarchy.

The lemma was formulated and proved by Kurt Gödel in his proof that the axiom of constructibility implies GCH.

References

• 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
  
  My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 (theorem 5.2 and lemma 5.10)

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