On ordinals accessible by infinitary languages
Saharon Shelah, Pauli Väisänen, Jouko Väänánen · Fundamenta Mathematicae · 2005
Let $\lambda$ be an infinite cardinal number. The ordinal number $\delta(\lambda)$ is the least ordinal $\gamma$ such that if $\phi$ is any sentence of $L_{\lambda^+\omega}$, with a unary predicate $D$ and a binary predicate $\prec$, and $\phi$ has a mo