$\sigma$-Ideals and outer measures on the real line

S. García-Ferreira, A. H. Tomita, Y. F. Ortiz-Castillo

A {\it weak selection} on $\mathbb{R}$ is a function $f:[\mathbb{R}{]}^2\to \mathbb{R}$ such that $f(\{x,y\})\in \{x,y\}$ for each $\{x,y\}\in [\mathbb{R}{]}^2$. In this article, w…