Cardinal invariants of universals
نویسندگان
چکیده
We examine when a space X has a zero set universal parametrised by a metrisable space of minimal weight and show that this depends on the σ-weight of X when X is perfectly normal. We also show that if Y parametrises a zero set universal for X then hL(X) ≤ hd(Y ) for all n ∈ N. We construct zero set universals that have nice properties (such as separability or ccc) in the case where the space has a K-coarser topology. Examples are given including an S space with zero set universal parametrised by an L space (and vice versa).
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