# diagonal intersection

If $\langle S_{i}\rangle_{i<\alpha}$ is a sequence then the diagonal intersection, $\Delta_{i<\alpha}S_{i}$ is defined to be $\{\beta<\alpha\mid\beta\in\bigcap_{\gamma<\beta}S_{\gamma}\}$.

That is, $\beta$ is in $\Delta_{i<\alpha}S_{i}$ if it is contained in the first $\beta$ members of the sequence.

Title diagonal intersection DiagonalIntersection 2013-03-22 12:53:17 2013-03-22 12:53:17 Henry (455) Henry (455) 5 Henry (455) Definition msc 03E99 diagonal intersection