Diamond, GCH and weak square
Diamond, GCH and weak square
Shelah proved recently that if $\kappa >\omega$ and $S\subseteq \kappa ^+$ is a stationary set of ordinals of cofinality different from $\mathrm {cf}(\kappa )$, then $2^\kappa =\kappa ^+$ implies $\Diamond _{\kappa ^+}(S)$. We show that for singular $\kappa$, an elaboration on his argument allows us to derive $\Diamond _{\kappa ^+}(T)$ …