What is the Pacman lemma?

Question

I've seen "the Pacman lemma" mentioned in the context of reduction orderings on logical terms, but a Google search doesn't find a definition; what exactly is it? Closest a search found was a "Pacman rule" in the context of calculus; is that the same thing?

Answer 1

Lemma. : Let $(X,\mathcal{S})$ be a measurable space, $\nu$ a signed measure. Suppose we have a subset $E \in \mathcal{S}$ and $0 < \nu(E) < \infty$ . Then, there exists a positive set $P \subset E$ such that $\nu(P) > 0$.

I found it here:

• http://www.math.unl.edu/~s-bbockel1/921-notes/Signed_Measures.html