Published online by Cambridge University Press: 19 June 2017
Given a scattered space   $\mathfrak{X} = \left( {X,\tau } \right)$  and an ordinal λ, we define a topology
 $\mathfrak{X} = \left( {X,\tau } \right)$  and an ordinal λ, we define a topology   $\tau _{ + \lambda } $  in such a way that τ +0 = τ and, when
 $\tau _{ + \lambda } $  in such a way that τ +0 = τ and, when   $\mathfrak{X}$  is an ordinal with the initial segment topology, the resulting sequence {τ +λ}λ∈Ord coincides with the family of topologies
 $\mathfrak{X}$  is an ordinal with the initial segment topology, the resulting sequence {τ +λ}λ∈Ord coincides with the family of topologies   $\left\{ {\mathcal{I}_\lambda} \right\}_{\lambda\in Ord} $  used by Icard, Joosten, and the second author to provide semantics for polymodal provability logics.
 $\left\{ {\mathcal{I}_\lambda} \right\}_{\lambda\in Ord} $  used by Icard, Joosten, and the second author to provide semantics for polymodal provability logics.
We prove that given any scattered space   $\mathfrak{X}$  of large-enough rank and any ordinal λ > 0, GL is strongly complete for τ  +λ. The special case where
 $\mathfrak{X}$  of large-enough rank and any ordinal λ > 0, GL is strongly complete for τ  +λ. The special case where   $\mathfrak{X} = \omega ^\omega + 1$  and λ = 1 yields a strengthening of a theorem of Abashidze and Blass.
 $\mathfrak{X} = \omega ^\omega + 1$  and λ = 1 yields a strengthening of a theorem of Abashidze and Blass.