The Nikodym property and filters on $\omega$. Part II

Seminarium: 
Topologia
Osoba referująca: 
Tomasz Żuchowski (UWr)
Data: 
wtorek, 23. Kwiecień 2024 - 17:00
Sala: 
A.4.1 C-19 (Politechnika Wrocławska)
Opis: 
In this talk we will continue studying the family $\mathcal{AN}$ of ideals on $\omega$ presented in the Part I. Recall that $\mathcal{I}\in\mathcal{AN}$ iff there exists a density submeasure $\varphi$ on $\omega$ such that $\varphi(\omega)=\infty$ and $\mathcal{I}\subseteq Exh(\varphi)$. We will present several conditions for a density ideal $\mathcal{I}$ equivalent to the fact that $\mathcal{I}\in\mathcal{AN}$. Next, we will make an analysis of the cofinal structure of the family $\mathcal{AN}$ ordered by the Katetov order $\leq_K$. We will prove that there is a family of size $\mathfrak{d}$ which is $\leq_K$-dominating in $\mathcal{AN}$, but there are no $\leq_K$-maximal elements in $\mathcal{AN}$.