Yasuo Yoshinobu

Learn More
It is known that the Stone-ˇ Cech compactification βX of a non-compact metrizable space X is approximated by the collection of Smirnov compactifications of X for all compatible metrics on X. We investigate the smallest cardinality of a set D of compatible metrics on the countable discrete space ω such that, βω is approximated by Smirnov compactifications(More)
We present several forcing posets for adding a non-reflecting stationary subset of Pω 1 (λ), where λ ≥ ω 2. We prove that PFA is consistent with dense non-reflection in Pω 1 (λ), which means that every stationary subset of Pω 1 (λ) contains a stationary subset which does not reflect to any set of size ℵ 1. If λ is singular with countable cofinality, then(More)