Weak $\lambda$-sets and almost-normal Isbell-Mrówka spaces

César Ismael Corral Rojas, Vinicius de Oliveira Rodrigues, Victor dos Santos Ronchim

We determine the least cardinality of a set of reals that is not a weak $\lambda$-set, proving that it is $\max \{\mathfrak{b},\mathfrak{s}\}$, where $\mathfrak{b}$ and $\mathfrak{s}$ are the…