Specialising Trees With Small Approximations II

Abstract

We show that the existence of a well-known type of ideals on a regular cardinal $\lambda$ implies a compactness property concerning the specialisability of a tree of height $\lambda$ with no cofinal branches. We also use Neeman's method of side conditions to show that the existence of such ideals is consistent with stationarily many appropriate guessing models. These objects suffice to extend the main theorem of \cite{mhpr_spe}: one can generically specialise any branchless tree of height $\kappa^{++}$ with a ${<}\kappa$-closed, $\kappa^{+}$-proper, and $\kappa^{++}$-preserving forcing, which has the $\kappa^+$-approximation property.