Let be an ideal on . For we write if for all with some . Moreover, we denote \mathcal{D}_{\mathcal{I}}=\{f\inω^ω: f^{-1}[\{n\}]\in\mathcal{I} \text{ for everyn\in ω}\} (in particular, denotes the family of all finite-to-one functions). We examine cardinal numbers and describing the smallest sizes of unbounded from below with respect to the order sets in and , respectively. For a maximal ideal , these cardinals were investigated by M. Canjar in connection with coinitial and cofinal subsets of the ultrapowers. We show that for all ideals with the Baire property and that for all coanalytic weak P-ideals (this class contains all ideals). What is more, we give examples of Borel (even ) ideals with as well as with .

生成讲解博客的中文版本

生成AI智能校验的中文版本