On $\pi$-compatible topologies and their special cases

TL;DR

This paper investigates $\pi$-compatible topologies and admissible extensions, revealing new properties and relationships, and clarifying their roles in the structure of topological spaces.

Contribution

The paper introduces new results on $\pi$-compatibility and admissible extensions, expanding understanding of their properties and specific cases in topology.

Findings

$\pi$-compatible topologies share the same nowhere dense and meager sets.

Admissible extensions occur frequently in literature and have specific structural properties.

New theorems about the nature and examples of $\pi$-compatibility and admissible extensions.

Abstract

Topologies $\tau, \sigma$ on a set $X$ are called $\pi$-compatible if $\tau$ is a $\pi$-network for $\sigma$, and vice versa. If topologies $\tau, \sigma$ on a set $X$ are $\pi$-compatible then the families of nowhere dense sets (resp. meager sets or sets possessing the Baire property) of the spaces $(X, \tau)$ and $(X, \sigma)$ coincide. A topology $\sigma$ on a set $X$ is called an admissible extension of a topology $\tau$ on $X$ if $\tau \subseteq \sigma$ and $\tau$ is a $\pi$-network for $\sigma$. It turns out that examples of admissible extensions were occurred in literature several times. In the paper we provide some new facts about the $\pi$-compatibility and the admissible extension as well as about their particular cases.